Remove NullPointer errors generated if PVName formula is null
Remove duplicate colour ids from file

- this change brings the test/resources file in line with org.csstudio.opibuilder.converter/html/sample_edl_files/colors.list
Extend EDM Converter to handle MenuMux widgets
Merge remote branch 'dls-github/CSS75_colourlist'
Merge remote branch 'dls-github/CSS74_null_pointer'
Merge remote branch 'dls-github/converter_menumux' into converter-edm
Merge branch 'converter-edm'