RGB Matrix: if a head includes a dimmer channel, it will be controlled by a RGB Matrix

UI: Fixed QLC+ website URL click event
Reviewed all the fixtures with heads to include a dimmer channel
Updated docs
error in qlcchannel_test
some more fixes in tests
Merge pull request #204 from tornel/error-in-test

Fixed qlcchannel and aboutbox test units
Added fixtures: Clay Paky A.LEDA Wash K5, Clay Paky A.LEDA Wash K10, Clay Paky A.LEDA Wash K20
Added heads to Clay Paky fixtures
Allow VC sliders to control RGB matrices