RFR: 8279396: Define version in .jcheck/conf

[Kevin Rushforth]

This patch adds the version property to `.jcheck/conf`. By doing this we can remove the corresponding configuration from the Skara bots, which in turn reduces the need for timing and general complexity of starting a new JavaFX release. See openjdk/jdk#6929 for the similar PR for the `jdk` repo.

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Commit messages:
 - 8279396: Define version in .jcheck/conf

Changes: https://git.openjdk.java.net/jfx/pull/706/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=706&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279396
  Stats: 8 lines in 2 files changed: 8 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/706.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/706/head:pull/706

PR: https://git.openjdk.java.net/jfx/pull/706