RFR: 8272870: Add convenience factory methods for border and background

[Nir Lisker]

Added convenience factory factory methods for Background and Border.

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

Commit messages:
 - Reverted import organization
 - Added convenience factory methods

Changes: https://git.openjdk.java.net/jfx/pull/610/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=610&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272870
  Stats: 28 lines in 2 files changed: 28 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/610.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/610/head:pull/610

PR: https://git.openjdk.java.net/jfx/pull/610