GH-440 Remove annoying "Reading environment variable" messages
(maint) small update and formatting
(GH-426) Chocolatey-List waits on events to finish before return

Before this the events were not waiting before they returned back to other
functions, which was causing Collection modified errors if the collection was
still being added to when the next function was attempting to use the list.
(GH-426) Chocolatey-List should include prerelease when querying local

If you have prereleased items installed, it should always query those packages
for versions.
(GH-426) Ensure Chocolatey-List return type
(GH-426) Chocolatey-List get exit code
(maint) formatting
(GH-446) Remove Invoke-ChocolateyFunction

Now that we have the main commands wrapped with a try catch and non-zero exit
code, we don't need to funnel everything through this any longer, which
makes code readability better and actually fixes at least one bug
(Chocolatey-Verison was not throwing errors on non-existing packages due to
invocation always being through a function).
(GH-445) Chocolatey-Version improvements

This should help improve the functionality of chocolatey-version by setting it
to use the improved Chocolatey-List should speed some things up.

The perf when calling cver all is still going to be just as bad, there are
minor improvements but it makes a call to nuget for every package to check
for a newer version because nuget is limited in what you can pass to it. This
should have significant improvements when we change over to using pkg indexes
as they will be almost instantaneous returns.
Merge branch 'stable'