RFR: Introducing markdown

[Jesper Wilhelmsson]

Fixed a few bugs from html to markdown conversion.

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Commit messages:
 - Fixed page title and minor bugs from html to markdown conversion.
 - Converted all html files to markdown
 - Moved files to src directory
 - Changed mode on image.
 - Populating the repo with the old html guide files.

Changes: https://git.openjdk.java.net/guide/pull/4/files
 Webrev: https://webrevs.openjdk.java.net/guide/4/webrev.00
  Stats: 1840 lines in 23 files changed: 1840 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/guide/pull/4.diff
  Fetch: git fetch https://git.openjdk.java.net/guide pull/4/head:pull/4

PR: https://git.openjdk.java.net/guide/pull/4