add WMS GetCapabilities 1.0.0 parser

add a WMS GetCapabilities parser for version 1.0.0 as discussed with @cedricmoullet

The inheritance chain is a bit weird, since 1.0.0 inherits from 1.1.0, but this was really the easiest way to get this support in. Also, it's hard to find a good name for a base class that covers 1.1.X and 1.3.X versions, so I went with the other solution instead.

TIA for any review.