[FEATURE] Index scheduler task should run on read only file systems

[johfeu]

Currently the tasks breaks if localconf is not writable which makes it impossible to use this extension on instances with locked file systems.
Check for write permissions is not needed in all cases and should only be triggered if there is a need to write to localconf file (settings change).

Use case:
Read new labels of updated extensions while no settings change was made.

Maybe even the "ConfigurationChanged" could be done in a different way without writing to localconf at all?