Add __virtual__ functions for pecl and pip states

Similar to what was recently done for npm, disable pecl and pip states
when the needed binary is not available. This prevents tracebacks when
one tries running these states without the required shell command
installed.
Better documentation for npm, pecl, and pip states

This commit adds additional info to the top docstring for these states,
including SLS examples for how to properly set up requisites to ensure
that npm/pecl/pip is installed before these states are run.
Merge pull request #6149 from terminalmage/docs

Fix typo in top.sls docs
Merge pull request #6150 from terminalmage/docs

Clarify returner docs
Merge pull request #6147 from terminalmage/quickfix

Add __virtual__ functions for pecl and pip states
Add notice that this script is not up to date.
Remove links to very old versions of Salt Windows
Merge pull request #6152 from UtahDave/develop

Add notice about Windows Installer script. Remove older versions of Windows installer.
Use package name instead of full package

Fixes #6078
Using the package name instead of the full package name allows
for proper comparison.

This fixes pkg.version and pkg.latest on Windows
Fixup some Windows servermanager docstrings
Merge pull request #6155 from UtahDave/fix_win_doc

Fixup some Windows servermanager docstrings
Merge pull request #6154 from UtahDave/develop

Use package name instead of full package name
Make cmd state docs a little prettier

The current rst in the initial docstring for this state results in
oddly-formatted sphinx docs. This commit improves the formatting.