Improve FASTA Download

[enuggetry]

Currently, FASTA download can take a long time to process before downloading takes place. This is understandable given the use of blastdbcmd to extract the FASTA data. However, during the processing, the app is hung while waiting for the processing. I'd like to see it display a progress indicator while it is waiting, as it can take several minutes to process. Or, it can somehow do this processing in the background. (not a high priority. Just a suggestion)

[yeban]

I agree the UI shouldn't hang while waiting for the download and should probably show a progress indicator as the download can indeed take a while. I would also like any error during download to be displayed in the standard error modal instead of navigating to a new page.

I think this is a kind of enhancement that can be included in a point release after 2.0 stable.