install docs upgraded to Wildfly 8.1.0.CR2

this is necessary due to a bug in jackson provider related to ContextResolver:
https://community.jboss.org/thread/237728

also added hibernate module to jackson to ease the serialization of
lazily initialized properties
renamed util.test package
'not found' exception handler
user endpoint for basic user data
user avatar: sending the file back
using PekSuccess instead of a bare entity
formatted Membership, removed uncessary interface
api endpoint framework refactor

Using exceptions (PekWebException and co) for recoverable application
errors, for example when an entity is not found.

Using a central response wrapper for wrapping successful request in
a PekSuccess instance (to have a unified response structure). This allows
us to return _bare_ values from api endpoint methods.
added tests for avatar endpoint
Merge pull request #102 from kir-dev/users

api basics, user api endpoint