Added Blockchain Bootstraping Tutorial

Per @laanwj request in #3724

Fixing Checkpoints Comment

Fixed Image Paths

Removed requirement.

Update Torrent Links.

Update Links 2

Link would not work.

2 Small Fixes

Changed in to from

@laanwj suggestion on safety
refactored bootstrap info for doge infra and screenshots
Changed UI to pink.
Changed transaction description dialog to pink background (appears not to inherit background from bitcoingui.cpp).