vxJS.xhr.use() no longer merges the second, third and fourth argument,
but instead replaces the old ones with the new ones; added getters for
the various parameters;
before that xhrForm() would still submit previously
checked/submitted/unchecked checkboxes; updated xhrForm() and
autoSuggest() to reflect these changes

Change-Id: I2b05350a04292ca312e9a29eeca777d54a86b502