[jfx18] RFR: 8279345: Realign class docs of LightBase and subclasses

[Nir Lisker]

Now that the standard concrete light types were added, there is an opportunity to rearrange and rewrite some of the class docs. Here is a summary of the changes:

* Moved the explanations of attenuation and direction up to `LightBase` since different light types share characteristics. `LightBase` now contains a summary of its subtypes and all the explanations of the properties/characteristics of the lights divided into sections: Color, Scope, Direction, Attenuation.
* Each light type links to the relevant section in `LightBase` when it mentioned the properties it has.
* Added examples of real-world applications for each light type.
* Consolidated the writing style for all the subclasses.

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

Commit messages:
 - Updated copyright years
 - Initial commit

Changes: https://git.openjdk.java.net/jfx/pull/717/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=717&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279345
  Stats: 149 lines in 5 files changed: 93 ins; 26 del; 30 mod
  Patch: https://git.openjdk.java.net/jfx/pull/717.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/717/head:pull/717

PR: https://git.openjdk.java.net/jfx/pull/717