Alignments containing one or more protein sequences can be classed as nucleotide

Reported via twitter/gitter.

Jalview will disable protein shading/analysis options for alignments when it calculates that the proportion of the *total* number of symbols classed as nucleotides is greater than 85% (thanks [~gmungoc] for spotting that). This calculation is performed once on alignment creation, and merges all sequences together.

As a result, input files containing proteins and nucleotides, or containing proteins with low complexity regions may be misidentified.