Serve static assets under /ipwbassets from a directory

[ibnesayeed]

As per #528 adding a new route /ipwbassets/<path:path> and serving all the static assets from there. Some resources have already been moved to it and gradually we will get rid of the WebUI route and folder along with all the associated code in replay. When merged, close #528.

[codecov]

Codecov Report

Merging #529 into master will increase coverage by 0.51%.
The diff coverage is 21.42%.

@@            Coverage Diff             @@
##           master     #529      +/-   ##
==========================================
+ Coverage    23.3%   23.81%   +0.51%     
==========================================
  Files           6        6              
  Lines        1163     1138      -25     
  Branches      174      167       -7     
==========================================
  Hits          271      271              
+ Misses        875      850      -25     
  Partials       17       17

Impacted Files	Coverage Δ
setup.py	0% <ø> (ø)	⬆️
ipwb/replay.py	14.35% <21.42%> (+0.53%)	⬆️

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[ibnesayeed]

Now we got rid of the /webui route and corresponding folder while utilizing recently added asset serving endpoint. We have also moved index.html to templates and no longer performing find and replace.

[machawk1]

Tested and all LGTM