* README: Correct the general information so that it can also be used
	for the main page.
	* docs/Makefile.am: Add libgda-uimm.h to the list of files to be
	processed for documentation because the Doxygen main page will be
	contained there.
	* docs/reference/Doxyfile.in: Make the options coincide with the
	glibmm options.
	* libgda-ui/libgda-uimm.h: Add the main page.