RFR: Introducing markdown

[Jesper Wilhelmsson]

Converted all html files to markdown and added a makefile to build the html.

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Commit messages:
 - 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/3/files
 Webrev: https://webrevs.openjdk.java.net/guide/3/webrev.00
  Stats: 1837 lines in 23 files changed: 1837 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/guide/pull/3.diff
  Fetch: git fetch https://git.openjdk.java.net/guide pull/3/head:pull/3

PR: https://git.openjdk.java.net/guide/pull/3