ShaderCache should release its graphics resources

For the shader programs that it manages.

Change-Id: Ibddc8442cad1f1a652edc2277a37b5284f1283d2
Removed unnecessary call and added notes

Change-Id: I9b09ceba1ef624163d0199d59d05678e8b8f0e83
Let shader cache invoke release graphics resources on shader

Change-Id: Ic5820a41b4e75d66e5396054f20ab4f961107572