removing 'permissions' from valid update keywords for role update, moving manager functionality out of authorization.py, removing duplicate declaration of permission operation constants in permission.py and adding missing unit tests
Reverting previous commit to prepend commit message with bug id.

This reverts commit 73db3b709417db4ac0e34819f59979917515a0c3.
1066040 - removing 'permissions' from valid update keywords for role update,
moving manager functionality out of authorization.py, removing duplicate declaration of permission operation
constants in permission.py and adding missing unit tests
incorporating PR feedback
incorporating PR feedback
reverting change to use IndexError instead of validation since it does not raise an error for negative values
Merge pull request #820 from pulp/skarmark-1066040

removing 'permissions' from valid update keywords for role update, moving manager functionality out of authorization.py, removing duplicate declaration of permission operation constants in permission.py and adding missing unit tests