Add new command applet
command: Use GSettings signals to manage command/interval
command: UI improvements
command: Define max lenght for output of the command
command: Fix typo
command: Add comments and constants in code
command: Add support for output in GKeyFile (INI) format, allowing to change font and icon

The output of the command now can be in INI format, like:

[Command]
Output=MATE
Icon=mate

Output can be in pango format, icon need to be a stock name
command: Show the executed command as tooltip