ENHANCEMENT - add a diags command printing diagnostics info for choco.exe

[bcurran3]

Requesting a new command such as "diags" that could display choco version info, install location, Chocolatey cache location, nuget cache location, configured features (not a list of all of them), system state, validation checks, a quick check and report that the CRCs are OK on all Chocolatey files, a quick ping to the configured sources to check availability, etc.