Introduce EntryType, allowing to distnguish between:
- inherietd entries: Those inherit their values from
other entries, typcally system entries. They do not
allow overwriting the value, except row/col.
- system entries: those not created by the user in any way,
usually .desktop files in /usr/share/applications/...
- user entries: those that have been created by the user.
they can however also inherit, and overwrite inherited values.
inherited are used for the "favourites" feature.
