make external application chooser cells editable
* allows changing menu-name of the external application
* allows adding additional arguments to the application
add (add new entry) button to external applications editor
Merge branch 'editable_command_chooser' of https://github.com/Nanolx/phototonic into Nanolx-editable_command_chooser
Merge branch 'Nanolx-editable_command_chooser'
Minor changes to external app dialog