RFR: JDK-8289106: Add model of class file versions to core reflection

[Joe Darcy]

JDK-8289106: Add model of class file versions to core reflection

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

Commit messages:
 - Update phrasing.
 - Augment and correct docs.
 - Correct major versions; RELEASE_0 and RELEASE_1 are both 45.
 - Make major method public.
 - Add AccessFlag.locations(ClassFileFormatVersion)
 - Add ClassFileFormatVersion <-> Runtime.Version conversions.
 - Merge branch 'master' into JDK-8289106
 - JDK-8289106: Add model of class file versions to core reflection

Changes: https://git.openjdk.org/jdk/pull/9299/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9299&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289106
  Stats: 348 lines in 3 files changed: 346 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9299.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9299/head:pull/9299

PR: https://git.openjdk.org/jdk/pull/9299