Get "Simple key only" button working for lengths #361
Remove <b> from around min and max edit <input>s #361
Refactor text-value edit pages to share more code #361

The two pages that deal with multiple-choice characters now use the
same routine to save the values that the botanist changes on the page.
Remove unused JavaScript function #361
Refactor length-value editor to use common save #361

Now all three character-value editor pages use the same save() routine
and format their data the same way.
Fix #361 by adding length values to taxon editor

The character-value edit page for a taxon now not only shows the
multiple-choice values that are possible for the taxon, but also shows
and allows editing of length values.  This completes the refactoring
of the three character-value editing pages; they now all share common
code and logic, with the only difference being in how they are
initially rendered.
Merge branch 'feature/brandon-361'

Per #361, length values are now fully supported in the various
character-value editing pages for botanists beneath the /edit URL.