WKT lexer

As I found myself some spare time and enthusiasm, I tried to write a lexer to replace the regex-based parsing of WKT strings (see also #2172). Here is the result. Please let me know whether this is anywhere near the concepts that have been conceived.
I totally agree (both on the `ol.geom.GeometryType` and the 'ugly' part). So I definitely would like to give it a try to compare both builds. However, I got a bit stuck on the upper camel case used by `ol.geom.GeometryType`. Parsing the (typically uppercase) WKT's to camel case isn't very nice. Do you happen to know a simple workaround?