- Setting the generated tif as the group leader is removed. It screws up
the group, i.e. there is no leader anymore and sometimes removes CR2
file too.
- refactoring started.
Merge branch 'master' of https://github.com/yuhhey/Lua_hdr_darktable.git

Conflicts:
	luarc
	
	- Copy exif data from CR2 to tif with exiftool
	- Cleaning up
	- The removal of exported tifs can be configured.