RFR: 8223373: Remove IntelliJ IDEA specific files from the source code repository [v6]

[Thiago Milczarek Sayao]

> This PR does:
> 
> - Remove specific Idea files and let it be imported from gradle;
> - Adds checkstyle (to use with checkstyle plugin - it will let you know style mistakes);
> - Configures auto-format to sun style (with the changes mentioned in [Code Style Rules](https://wiki.openjdk.org/display/OpenJFX/Code+Style+Rules));
> - Automatically sets Copyright notice (updates year too);
> - Run configurations for samples/toys and builds.

Thiago Milczarek Sayao has updated the pull request incrementally with two additional commits since the last revision:

 - Update .gitignore
 - Remove unrelated gitignore

-------------

Changes:
  - all: https://git.openjdk.org/jfx/pull/1009/files
  - new: https://git.openjdk.org/jfx/pull/1009/files/e4c7b4ed..ec5d0ab1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1009&range=05
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1009&range=04-05

  Stats: 9 lines in 1 file changed: 0 ins; 9 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1009.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1009/head:pull/1009

PR: https://git.openjdk.org/jfx/pull/1009