chore: Unify python dependencies into requirements.in

[rafiu007]

This is WIP PR which takes care of dependency unification for the api server.

Checklist ::

• Move any test specific packages from requirements.in to tests/requirements.in
• Move any direct pip installations from Dockerfile.* to requirements.in
• Move any direct pip installations from tests/*.sh to tests/requirements.in
• Relative versioning in requirements.in & tests/requirements.in (no version pinning unless otherwise needed)
• Generate requirements.txt (not required) and tests/requirements.txt
• (Not Applicable)Update setup.py to use requirement.in
• Cleanup unused dependencies from requirements.in and tests/requirements.in (using pip install pipreqs)

[arajkumar]

@rafiu007 Could you please follow the template/checklist described in fabric8-analytics/fabric8-analytics-utils#57 (comment)?

[dgpatelgit]

I have added check-list template to PR description, @rafiu007 can you check and update the list as per code changes?

[arajkumar]

Also Dockerfile.tests should be modified to install pip packages from tests/requirements.txt

[arajkumar]

Just started reviewing :)

[arajkumar]

lgtm

@rafiu007 Please wait for one more approval.

[dgpatelgit]

LGTM

[deepak1725]

lgtm