loaders: Consider colorspaces (#838)

loaders: Consider colorspaces (#838)

* common: added colorSpace() function

This patch introduces colorSpace() function for SW and GL engine.

* infra: change LoadModule:read() into LoadModule:read(uint32_t colorspace)

This patch changes LoadModule:read() into LoadModule:read(uint32_t colorspace)

* picture: implement passing colorspace into loader

This patch implements passing colorspace into loaders.
Loader->read is now called on the first update.

* external_jpg_loader: support colorspaces

* external_png_loader: support colorspaces