make wsgi_eager.py the default

@VikParuchuri  @rocha 

This is to make the default wsgi.py eagerly read the POST parameters, to resolve a problem in nginx for large POSTs.

This solves the problem mentioned in https://edx-wiki.atlassian.net/browse/OEE-137

(all this PR does on top of the previous one is to make wsgi_eager.py the standard wsgi.py, which is the case for xqueue)