Updated git ignore to include .swp temp files
Added several simple modules that can be used to test the build system.

dd_dtype, ff_jk and both mux modules should compile and elaborate fine. reg_shift is
currently broken pending investigation.
 On branch dev_ben
 Changes to be committed:

	renamed:    src/rtl/mux.vhd -> mux_2to1.vhd
	new file:   src/rtl/ff_dtype.vhd
	new file:   src/rtl/ff_jk.vhd
	new file:   src/rtl/mux_4to1.vhd
	new file:   src/rtl/reg_shift.vhd