Discourage (ab)use of H1s, and relabel them

Re-label the headings in the MWFormatDropdownTool with MW-specific
headings per bug 43334, reduce the size of the dropdown's contents a
little to make the headings less vibrant, and move the H1 option to the
end of the list to further discourage its use.

Note that there are some issues with the underlying structure here and our
ability to split the repos into VE-core and VE-MW will need this to be
refactored.

Bug: 43334
Change-Id: I5a58b4dcebd6ceae0ffcd24f663429f25bdc3db9