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
Use popover from Bootstrap
Creating a resources folder for use by examples and API docs
Use map.on instead of map.addEventListener
Start a maximum of two new tile downloads per frame
Move configuration of maximum tiles loading into map.js
Correct link to example source
Merge pull request #471 from tschaub/example-typo

Correct link to example source
Update overlay example tags and doc
Quote object keys to prevent renaming in ADVANCED_OPTIMIZATIONS mode
Disable kinetic when multiple touches on screen
Merge pull request #466 from fredj/popover

Use popover from Bootstrap
Remove unused local variable
Merge pull request #474 from fredj/misc

Remove unused local variable
Redefine ol.Coordinate to be Array.<number>
Use slice to extract sub-arrays
Add ol.vec.Mat4.multVec2
Use ol.vec.Mat4.multVec2