Do not crash when Fqsen parsing fails

[Ocramius]

As discussed with @sebastianbergmann (sebastianbergmann/phpunit#3718), type annotations like array<foo, bar> and other more complex definitions currently lead to the phpdocumentor tooling to throw exceptions.

While it would be good to support these in full, this currently prevents picking up this tool at all in downstream consumers.

The suggestion is therefore to

1. Suppress Fqsen parsing errors
2. Improve upstream Fqsen parsing tooling not needed: see Migrate to better type inference tooling to detect BC breaks in types #143
3. Adapt covariance/contravariance checks to support more complex types moved to Migrate to better type inference tooling to detect BC breaks in types #143
4. Extract covariance/contravariance checks to a new namespace/library that only does that, making it easier to upgrade its capabilities moved to Migrate to better type inference tooling to detect BC breaks in types #143

[Ocramius]

Incomplete tasks deferred to #143