[UWS,TAP] 3 MAJOR DEPENDENT FIX: improve significantly the parameters...

[UWS,TAP] 3 MAJOR DEPENDENT FIX: improve significantly the parameters extraction from HTTP request in UWS (1) AND move the file-upload ability into the UWS library (2) AND the modification of parameters in UWS is now conform with the standard (3). (1) Only application/x-form-urlencoded content-type was supported. However a UWS must accept a request body containing only an XML document as a single byReference parameter. It is now done when the content-type is not known. (2) Besides multipart/form-data is now fully supported in UWS and so is still possible in TAP. (3) In the UWS standard, parameters can not be added after creation: they can just be modified. This rule is now respected in the UWS library.