In addition to increasing customizability this change makes it clear that the _working directory_ property only concerns the intial working directory and is not updated if the contained process changes its directory.

Note that setting the intial working directory is broken in upstream _QMLTermWidget_ and the appropriate patch [1] is not merged at the time of this commit.

[1]: https://github.com/KnairdA/qmltermwidget/tree/initial_working_directory_fix

Exposing access to the working directory to QML is the first step towards enabling usage analogously to a normal terminal emulator alongside the management of multiple running appications.
i.e. executing `cd` should change the global working directory so that consecutive commands work as expected.

Default keyboard shortcut for reset action was changed to `r` while the new kill action was bound to `d`.

Previously `kill` merely destroyed the terminal widget. This is contrary to the expected notion of `kill`, i.e. actually killing the process explicitly instead of relying on side effects.

The normal mode `d` verb now explicitly destroys the current item's content, be it a terminal widget or a history view.

`TerminalItem`'s `reset` member method wrongly performed a visual selection change which led to inconsistency when calling `kill` on a non-selected index.
Visual selection update is now performed on history view instantiation.

Otherwise one can not easily enter more complex shell commands such as pipe chains and so on.
The goal of _MetaTerm_ is not to implement a new shell language but to facilitate existing ones which is why this is best deferred to an existing application.

If a non-interactive applications terminates the next item is automatically selected in insert mode as to make the behaviour in this context more simmilar to normal shells.
Normal mode has to be entered explicitly for the highlighting to update on `HistoryViewer` instantiation.

Child processes of _MetaTerm_ may be terminated using other ways that the integrated kill command.
Automatic terminal widget destruction in such a event prevents the user from viewing the output of non-interactive applications.
This requires _MetaTerm_ to display the application's output after it was terminated.
This requirement is implemented via the new `HistoryViewer` widget that is instantiated after the terminal widget instance has been destroyed.

i.e. serialize objects to JSON.

Trailing whitespace was falsely recognized as a separate argument and as such led to resetting configuration values without obvious cause.

This enables the user to straight forwardly change all application settings via command mode.

During the implementation of this change I discovered that the way I was passing around `StateHandler` and `SettingsHandler` instances using properties was unnecessary. If all object instances are created in a common hierarchy they can access each other by their `id` property - i.e. `settings` and `mode` are available to the whole application without property trickery.

Otherwise they are not accessible to JS commands, i.e. they can not be changed in command mode.

`list` holds the components of the central list UI element.
`command` holds the UI and implementation parts of the command mode.
`widget` holds more or less general purpose elements that may also be of use in other circumstances.

This suggested adding an `iterate` helper method to `TerminalList` as well as line break logic to the command output log.

While `color` would obviously be the correct type to store a color value it is serialized as a `QVariant` value which is not easily changeable by the user.
This requirement is satisfied by `string` and as such this type is - at this point in time - a superior replacement of `color`.
Should the QML settings module be changed to serialize color values in a human readable fashion these types should be changed back to their formally correct value.

`output` text item reference is passed to all command implementations.

Requires new `executed` signal in `CommandInput` component to correctly trigger the state change.

Requires type dependent conversion in TerminaList's `selectItem` method as values passed through `eval` are of type `QJSValue` which is not implicitly convertible to Int.

Moved command implementation into separate ressource.
Commands are plain JavaScript functions in this separate ressource and as such callable via a simple call to `eval`.
Introduced the concept of a command prefix to enable implementation of e.g. a search command analogously to _vim_.