Update README.md
Support rendering ProjectDocumentationWidgets

Project documentation widgets can now be added to pages by adding an element with a data-documentation-widget='project-id' attribute.
The documenation content is looked up from the Spring Framework web server using a JSONP call.
Refactoring ProjectDocumentationWidget
Refactored ProjectModel

[#52044647]
Projects can now add documentation and quickstart widgets

[#52044647]
Quickstart and documentation widgets now use main site URL for API

[#52044647]
Updated index-common with latest layout and design [#54260788]
added updated iconsprite
Updated project metadata API URI

[#52044647]
Fixed rendering of documentation widgets if no active item on page
Use styled HTML for documentation widgets

[#55151702]
Switch to using javascript widgets using site styling

- Quickstart selector is implemented using bootstrap-select rather than the dropdown button used elsewhere
- Quickstart selector is still to be styled
Added bootstrap select for quick start

[#52044647]
Fixed JS for item slider
Fixed API endpoint URL for js quickstart and documentation widgets
Move README.md in case it clashes
Make widgets work on index common page
Extract project specific stuff to layout on home page
Extract right.md as an include
Fix right column