Add --use-wheel option to pip module/state

Refs #6777.
Also reload python's `site` module which handles `site-packages`.

In case a package has been installed into the current python process 'site-packages', the 'site' module needs to be reloaded in order for the newly installed package to be importable.
Add version checking for use_wheel in pip state
The site reload needs to be done on the state module refresh routine.
Fix OSError when roots file hash hasn't been built

When the fileserver updates, if no files have been served up then there
will be no hash file. Silently handle the exception to keep it out of
the log.
windows-package-manager.rst: remove nonsensical line
Add version check for use_wheel in pip module
Merge pull request #6867 from holmboe/develop

Ignore Vagrantfile
Merge pull request #6868 from terminalmage/issue6777

Add --use-wheel option to pip module/state
Merge pull request #6871 from s0undt3ch/features/states-reload

Also reload python's `site` module which handles `site-packages`.
Merge pull request #6872 from terminalmage/roots-update-fix

Fix OSError when roots file hash hasn't been built
Merge pull request #6873 from cvrebert/patch-2

windows-package-manager.rst: remove nonsensical line
Raw strings in regex compare to keep pylint happy
Merge pull request #6874 from terminalmage/issue6777

Raw strings in regex compare to keep pylint happy
Add the CLI example to the `pip.version` module function.
Merge pull request #6877 from s0undt3ch/develop

Add the CLI example to the `pip.version` module function.
Small documentation tweak, started out by replacing "it's" with "its" and added some other minor changes.
Correct the docstring for states.pip.installed

Should be >=1.4, not >1.4. Thanks @cvrebert!
Merge pull request #6880 from terminalmage/issue6777

Correct the docstring for states.pip.installed
Merge pull request #6879 from liyanage/develop

Small documentation tweak, started out by replacing "it's" with "its" and added some other minor changes.