Dependency updates, formatting and improvements

[javydreamercsw]

1. Updated to the latest NB maven plugins.
2. Added the lib folder as a local repository so project can be compiled without modifications after initial checkout.
3. Added some missing @OVERRIDES and fixed some formatting issues.

[javydreamercsw]

Why not? 8.1 is the latest version of the platform. Just keeping up to date with the platform.

[markiewb]

@javydreamercsw: You do not need to be up to date with the platform, when you do not use new API features.
For example: A plugin, which uses only official public NB6.x API can still be used in NB8.1. The NB devs take care of making the API backwards-compatible. It's the same with Java code. Code compiled years ago with Java 1.5 can still be run in a 1.8 VM.

[Revivius]

@javydreamercsw I think it is better to keep targeting 8.0.

[javydreamercsw]

So I guess I should revert that change then.