Uncertain stop codon in protein descriptions (fs and ext)

When a variant results in a frame shift or extension and we don't
see a new stop codon in the RNA, the protein description should use
the notation for an uncertain stop codon, e.g., `p.(Gln730Profs*?)`
instead of `p.(Gln730Profs*96)` where 96 is just the last codon in
our transcript [1].

To detect this, we now use `to_stop=False` in our `.translate()`
calls, since that will explicitely return `*` characters for stop
codons.

We also slightly fix the coloring of changes in the protein sequence
where previously changed stop codon characters where not included.

[1] http://www.hgvs.org/mutnomen/FAQ.html#nostop