RFR: Markdown anchors

[Jesper Wilhelmsson]

Found how to do link anchors in markdown. Added anchors in the glossary as well. Also changed to short hash in the
footer, the long hash took over the whole page in the final published version.

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Commit messages:
 - Markdown anchors

Changes: https://git.openjdk.java.net/guide/pull/13/files
 Webrev: https://webrevs.openjdk.java.net/guide/13/webrev.00
  Stats: 28 lines in 4 files changed: 0 ins; 0 del; 28 mod
  Patch: https://git.openjdk.java.net/guide/pull/13.diff
  Fetch: git fetch https://git.openjdk.java.net/guide pull/13/head:pull/13

PR: https://git.openjdk.java.net/guide/pull/13