[Security] + fixed typo in UnknownUserException
[Security] + added default value (:false) to User's api_key_enabled property
[Rest] + fixed typo in SecurityControllerTest
#149 - removed dependency to 'eric-chau/installers' package
Merge pull request #150 from backbee/149

close #149 - removed dependency to 'eric-chau/installers' package
REFS #143 - use BackBee/Utils inside BackBee
[ClassContent] + fixed CategoryManager coding style