BasicAnalyzerReference generates a lot of exceptions in error cases

[jaredpar]

In the case of a non-analyzer being passed to /analyze the implementation of BasicAnalyzerReference can lead to a lot of exceptions due to this code pattern:

assembly.GetTypes()

Every type that has a missing reference will generate a load event that throws a FileNotFoundException. In simple cases this can lead to 500+ exceptions trying to debug the compiler. Should use SRM here or pick a caching strategy in the load context.