add support for DSC_RESOURCE_PATH

[SteveL-MSFT]

PR Summary

If DSC_RESOURCE_PATH env var exists, we use that instead of PATH for resource discovery.

PR Context

Fix #133

[michaeltlombardi]

@SteveL-MSFT - so, to clarify, the only way to set this is to do either:

DSC_RESOURCE_PATH=/usr/mikey/resources dsc resource list

or

$env:DSC_RESOURCE_PATH = 'C:\Users\Mikey\resources'
dsc resource list

but not:

dsc --resource_path /usr/mikey/resources resource list

or

$ResourcePaths = @(
  'C:\Users\Mikey\resources',
  'C:\dsc_resources'
) -join ';'
dsc resource list --resource_path $ResourcePaths

This is an environment variable only override, not an optional argument?

[anmenaga]

LGTM

[SteveL-MSFT]

This is an environment variable only override, not an optional argument?

@michaeltlombardi Correct, this is by env var only