Enabling Markdown and other JSDoc improvements

This change enables GitHub flavored markdown for APIdoc
comments. The code example in map.js shows how to use markdown
for code snippets. doc/index.md is now included again as start
page for the docs. Everything in the doc/tutorials directory
will also be added to the docs as tutorial. As an example, I
moved the ol3.md file with the architecture to the tutorials
directory.

Currently properties and methods annotated with @inheritDoc
or @override won't be documented at all. This is a known issue,
so I added a custom JSDoc plugin with a hack to avoid this.
Use bootstrap layout and css from examples

I'm sure this can be made much prettier still, but at least we
have a common theme with the examples now.
Making social links work
Creating a resources folder for use by examples and API docs
Merge pull request #444 from ahocevar/jsdoc

Enabling Markdown and other JSDoc improvements. r=@marcjansen,@Turbo87