Fixes to includes and more

Due to use of protoc 2.6.1 I was able to find unnecessary includes in the proto files causing circular dependency problems. With some include removed it is possible to generate classes even without the dependency python script.

Furthermore the PR fixes a aliasing problem on Windows with the ERROR enum value.

The first commit contains a fix for enabling the protojs compiler per default. It may be a better solution to use the "?=" operator in the Makefile for some values. See: http://stackoverflow.com/questions/448910/makefile-variable-assignment