Added basic ol.parser.polyline module

This module will contain the low-level functions for Google's "Encoded
Polyline" algorithm.
polyline: Added decodeSigned/UnsignedInteger() functions
polyline: Added encode/decodeFloat() functions
polyline: Added encode/decodeFlatCoordinates() functions
Add ol.Extent.getForView2DAndSize
Use ol.Extent.getForView2DAndSize
Optimize ol.Extent.getForView2DAndSize
Add ol.renderer.Layer.snapCenterToPixel
Use snapCenterToPixel in Canvas renderer
Use snapCenterToPixel in WebGL renderer
Use snapCenterToPixel in DOM renderer
polyline: Added missing parenthesis for one-line statements
polyline: Renamed variables to camelCase convention
polyline: Only declare i variable once

Javascript only has function-wide scoping...
test/polyline: Added more test cases from official documentation

.. and marked those tests as such. URL of the "Encoded Polyline Algorithm Format" page is https://developers.google.com/maps/documentation/utilities/polylinealgorithm
test/polyline: Added two more test cases for unsigned integers

Again taken from the official documentation at Google.
polyline: Added encode/decodeUnsignedIntegers() functions
polyline: Added encode/decodeSignedIntegers() functions
polyline: Added encode/decodeFloats() functions
polyline: Added encode/decodeDeltas() functions