RFR: Fixed links

[Jesper Wilhelmsson]

* Cleaned up external links to be fully qualified links rather than relative links
* Changed links to Project definition from bylaws#_6 to bylaws#project
* Added missing links to keywords and JBS labels
* Increased section spacing to 2em

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Commit messages:
 - Fixed links

Changes: https://git.openjdk.java.net/guide/pull/32/files
 Webrev: https://webrevs.openjdk.java.net/?repo=guide&pr=32&range=00
  Stats: 18 lines in 2 files changed: 0 ins; 0 del; 18 mod
  Patch: https://git.openjdk.java.net/guide/pull/32.diff
  Fetch: git fetch https://git.openjdk.java.net/guide pull/32/head:pull/32

PR: https://git.openjdk.java.net/guide/pull/32