Drag n Drop: don't interpret elements dragged from our own page.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Drag n Drop: error reading files means it's not FASTA.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Drag n Drop: Remove dead code. Improved FASTA detection regex.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Drag n Drop: show error messages without any transition.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Drag n Drop: Overlay would show the last error message. Fixed it.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>