Append filename to shader names

Currently, when a shader fails to compile the error is hard to decipher since the name is just a unique identifier. This simply appends the source file name so we can at least identify which shader failed, keeping the benefit of efficient comparisons with the UID prefix.

I would have liked to add a string representation of the define map, but OSG actually uses shader name as the input for glObjectLabel which has a implementation dependent maximum length. Many of the existing define maps were too large in my case.