Merge pull request #1830 from twpayne/geom-fixes

Extra geometry functions
Use goog.math.lerp in ol.geom.flat.lineStringInterpolate
Use goog.math.lerp in ol.geom.flat.lineStringCoordinateAtM
Factor out ol.geom.flat.closest
Factor out ol.geom.flat.simplify
Factor out ol.geom.flat.interpolate
Factor out ol.geom.flat.length
Factor out ol.geom.flat.area
Factor out ol.geom.flat.orient
Factor out ol.geom.flat.contains and interiorpoint
Factor out ol.geom.flat.deflate
Factor out ol.geom.flat.flip
Factor out ol.geom.flat.inflate
Factor out ol.geom.flat.reverse
Move squaredDistance and squaredSegmentDistance into ol.math
Factor out ol.geom.flat.transform
Factor out ol.geom.flat.center
Remove empty ol.geom.flat
Remove old gml example
Remove old GML parser