Alignment View Start and End Position

[dacowan404]

Currently Alignment view only displays the full sequence when nucleotide is selected. For Codons or Amino Acids,users can select start position. Given the default dataset is 30kb, updates (such as show/hide characters/NTs) can sometimes be slow or fail due to limitations of canvas (increasing width exceeds max width of canvas). It should be fairly straightfoward to implement the start position for nucleotide data and implement a end position (or length) for all data types.