Check and warn if key specs are not met

[adrienlauer]

The following specs should be tested:

In core:

• jta.version 1.2 (optional)
• javax.annotation 1.2
• javax.validation 2.0.0
• javax.el 3.0.0 (optional)

In web:

• javax.servlet 3.0.0
• javax.websocket 1.0 (optional)

In rest:

• javax.ws.rs 2.1

[adrienlauer]

This can be a part of the validation tool #259 by implementing various ValidationProvider interfaces in the relevant plugins. The plugins could simply output a warning log in production mode for the violations but return the list of violations when the validate() method is invoked.