Evas GL common: Factorize shader generation code

Evas GL common: Factorize shader generation code

Remove all individual shaders, factorize everything into
one vertex and one fragment shader. All previous functionality
has been kept as is[*]. Some new features have been added
(new shader types).

This is a first step in simplifying and improving the shaders system.
Next: simplify shader selection

[*] Yeah, that's quite a bold statement here. Maybe I broke everything.