Formatting 2.3
Revert "Grouping the files into chapters."
This time trying to group in a new way. Earlier grouping was in sync with the current docs.

This reverts commit 52131179cdcacea2d4faf25ceaf2811646f38c57.
Restructuring the docs. First cut.
Cleaning the index page and concepts_in_go.
Removing google serch key.
* GitBook search will be used henceforth (assuming our eventual goal is to host the documentation on GitBook). Google search won't be used any longer.
Sanitizing configuration, installation and navigation directories.
#11 - Fixing the GitBook URL.
#10 - Making Work in Progress more evident.

Also, added link to current user documentation.
Fix typo
Wording
Lowercase folder name to match hyperlinks
gitbook config
Start fleshing out gitbook summary based on current Thoughtworks help
Fix links
Remove duplicated TOCs
Fix image references
Localise a few images to the user docs
Fixing inline hyperlinks
Remove spurious messages
Add some pages to the build