Added an option in setup.py to use any branch from azure-functions-host

[gavin-aguiar]

Added an option in setup.py to use any branch from azure-functions-host
Usage

python setup.py webhost
python setup.py webhost --use-branch=dev
python setup.py webhost --use-branch=abc/branch

Description

Fixes #

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PR information

• The title of the PR is clear and informative.
• There are a small number of commits, each of which has an informative message. This means that previously merged commits do not appear in the history of the PR. For information on cleaning up the commits in your pull request, see this page.
• If applicable, the PR references the bug/issue that it fixes in the description.
• New Unit tests were added for the changes made and CI is passing.

Quality of Code and Contribution Guidelines

• [x ] I have read the contribution guidelines.

[codecov]

Codecov Report

Merging #978 (9f4ab3c) into dev (6980e27) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev     #978   +/-   ##
=======================================
  Coverage   81.01%   81.01%           
=======================================
  Files          35       35           
  Lines        2339     2339           
  Branches      371      371           
=======================================
  Hits         1895     1895           
  Misses        337      337           
  Partials      107      107           

Flag	Coverage Δ
unittests	80.97% <ø> (ø)

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