Add support for setting forceAuth, comparisonType, bindingUri to the Saml2Client

The Saml2Client assumes default values for forceAuth (false), comparisonType and bindingUri (HTTP-POST). This patch allows the applications to customize these options.
They are not related. The IDP in its descriptor can specify the supported binding types and the SP should be able to use any of them. This is taken care of in the encoder. 

My understanding is, the IDP can also be configured to send response either via POST or GET. I have checked a couple of IDPs and they all use POST as the option. 

So to answer your question, the decoder is not affected by this change.