Resolve Doctrine proxies to real entity names in order to generate proper
identifiers for model.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT
Fixed model class resoultion when string representation given.
Added "doctrine/common" as requirement.
Updated version constraint for doctrine/common (from 2.3 to 2.2).
Merge pull request #40 from phansys/master

Resolve Doctrine proxies to real entity names