Added a Readme.md field for Repositories for a readme page using Markdown

Very similar to the readme.md page for github pages. For each repository
there is a new Readme property that is a string of markdown text that
describes the repository.  This could be used to describe the
dependencies, instructions and other information about the repository.
Added the MarkdownDeep nuget package to handle the transformation of
markdown text to Html.  The user interface includes a markdown toolbar,
help section and preview fields.
Reverted previous implementation of the readme.md. Instead when using the repo browser any .md file will be rendered in the resulting markdown formatted text using the MarkdownDeep library.  This will allow a more general handling of markdown files inside a repository and is a much simpler implementation.
Added detection of markdown files and rendering when using the repository browser. Reverted old readme sql script.
Merge pull request #180 from kengibous/master

Added a Readme.md field for Repositories for a readme page using Markdow...