Update ofShader.cpp to use logging modules

There were a number of logging messages produced by ofShader that did not have the module set to "ofShader". This update fixes most of these with really trivial changes. 

Unless I'm missing something, it appears that due to limitations in the ofLog interface there is no way to add module information to the ofLog messages that take a log level as an argument (as in the ofShader::checkShaderInfoLog() function). To do so would need a constructor for ofLog that takes a module string as an argument or something.