added private function for testing and setting

Added New private function __testappPool. This is called by
Test-TargetResource and Set-TargetResource.  It has an additional
parameter [switch]$update.  When its called from Test-TargetResource the
function just tests the settings. When its called from
Set-TargetResource an additonal parameter is sent ($update) and the
unmatched settings are updated.

Also added Pester tests.
Merge remote-tracking branch 'origin/master'

Conflicts:
	DSCResources/PSHOrg_cAppPool/PSHOrg_cAppPool.psm1