WxS_plugins: Adding 2 new filters to analyze WxS queries

This PR aims to provide 2 new filters that we are currently using internally at Camptocamp to parse specific WMS / WMTS queries (which stand for Web Map Service / Web Map Tile Service).

Due to the nature of the queries and the possible needs to convert into other spatial reference systems, it required to add a new dependency to manage the reprojection of the geographical coordinates: The gem used is called Geoscript, which makes use of Geotools Java library.

I provided some basic unit testing along with these two plugins.

Do not hesitate to give feedback in case I did something wrong, hoping you will find these 2 new plugins useful.

Best regards,

-- Pierre