Rewrite the GSettings tool.
Improvements/changes:
- simplify the code by performing common actions (like creating a
schema) in only one place instead of one per-command
- new features (list schemas, list keys, monitor multiple, etc)
- factor-out bash completion and implement in shellscript
- input validation: should never abort due to invalid inputs
Still to do:
- proper error checking for ranges/choices
- support for querying range/choice information
- bash completion support for enums
Closes bug #629289, possibly among others.
