Changes the way we gather request parameters.
I'd like to avoid methods with dozens of parameters. It's better to have
a immutable POJO that contains all the needed information than a lot of
parameters that goes from a method to the next.
Adds strict validation for all the mandatory parameters.
WMS now builds a GetMapParameters and then request a Map using it.
It's cleaner to do that this way...
Improves management of mandatory parameters in getFeatureInfo
They are now known statically so that we can check they are set in a
more concise way. They are tested too.
Finally adds GetFeatureInfo support. It only reply with plain text, but
it seems to be working.
Merge pull request #37 from agueganno/feature-info

Add basic support for GetFeatureInfo