UI: OS CRUD fn and tests

 This PR working fine with all tests.

what is done:
- arch tasks and tests are working fine
- added a helper function `select-entity` in Base class to select the entities(arch, os, ptable) either from checkbox list or from selecion list
- Updated set_parameter/remove_parameter as helper functions and moved them to Base and updated locators as well.
- Made changes to make the code pep8 compliant
- Added tests and methods for OS.

What is pending:
- results assertion
- support of updating provisioing layout

I'm thinking to cover these in next PR with search method.