Commandline interface for sosi.js

Both SOSI.js and SOSI_lite.js can be executed with nodejs on commandline to convert a SOSI file to any of the supported output formats. 
(SOSI_lite is still b0rken, but once it's fixed, the CLI support should work as well)

Minor changes that follow with this branch
- example viewer supports URLs 
- LineStringFromArc extends LineString