Request user to report 500 errors to admin or forum; remove not_found handler.

Any runtime error unless specifically handled is trapped as internal server
error (500) by SS and shown to the user with the full backtrace, requesting
them to report it to the admin of the SS installation or the public forum.

Removed not_found handler since it depended on 500.erb which I tweaked
specifically for 500 (internal server) errors. Sinatra, in production, shows a
page with heading (and only a heading) "No Found" for 404 errors which is
almost as good as what we previously had. We can install a more helpful 400
page later.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Inform users about network and server timeout errors.

Timeout or network errors previously appeared to the user as "a flicker of
spinner followed by no results or an empty modal", leaving them to figure
out for themselves what exactly happened. Not good.

Detecting timeout errors is tricky. We can be sure that the response will be
empty if server timed-out. But empty response can be caused due to myriad of
network issues.

So we check for empty response and notify users that either the server timed
out (and hence she should contact admin), or there's a temporary network issue
(and hence she should try again later). As a laster resort, the user should
seek help on the forum.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Round off bit score during display.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Pretty print evalue and right align numbers in tabular view.

Numbers look better when right aligned.

TODO: extract into formatting of evalue into a helper function.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Re-instate sequence retrieval per hit.

TODO:
1. Clicking on FASTA scrolls to top.
2. FASTA of all hits.
3. Download ability.
4. Simplify.

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