rawspeed: preliminary support for Panasonic DMC-GH4

http://darktable.org/redmine/issues/10204
http://bugzilla.rawstudio.org/show_bug.cgi?id=632

thanks to martin schitter

color matrix still needs to be confirmed via a .dng
rawspeed: add 7DmkII warning for the time being
rawspeed: add NX300M alias for NX300
adobe_coeff: add NX300M (same as NX300)
wb_presets: add NX300M (same as NX300)
colormatrices: add NX300M (same as NX300)
wb_presets: olympus e-m10 (thanks to PolarFox)