[ccss] Correctly initialise color properties.
[ccss] Correctly initialise color properties.

In ccss_color_create() the property's base class was initialised
manually instead of using ccss_property_init(). This lead to valgrind
complaining about jumps on uninitialised values in
ccss-stylesheet.c:482

freedesktop-unofficial-mirror/ccss,freedesktop-unofficial-mirror/ccss,freedesktop-unofficial-mirror/ccss