Identity improvements and code refactoring

Dependencies upgrade : 
- RESThub from 2.1.0 to 2.2.0-SNAPSHOT (waiting for a proper release)
- Spring security 3.2.4 to 4.0.0.M1 (also waiting for a proper release)

New features : 
- Start an all in one spring secured user/group/role management using spring profiles
- Basic parametrized interfaces for user/group/roles
- Basic parametrized implementations for user/group/roles
- Default implementation for spring profiles (resthub-identity-role, resthub-identity-group, resthub-identity-user)
- User authentication service added in UserDetailService

Updates : 
- Adding @Secured annotations with ROLE_ prefix for parametrized implementations
- Integration tests updated with spring security login request
- Adding login form in webapp
- Adding UserService specific implementation for demo purpose
- Maven dependencies managed in parent pom

Removed : 
- Generic named classes (renamed to parametrized implementations)
- Service interfaces from contract module (moved to core module)