Prevent overwriting unit definition
Reset all property units and warn on override
Remove virtual record_ functions never used
Fix re-setting a unit on the same camera class
Refactor out get_param_spec_by_name
Simplify test setup
Fix #41: add write accessibility API
Merge pull request #42 from ufo-kit/fix-41-access-specifications

Fix #41 access specifications
Fixed a crash in camera gui when loading of a camera plugin fails
mock: link m explicitly

Seems not to be the case on current Ubuntus.