Added PSH option to windows/local/ask exploit

Gives you the ability to use powershell to 'ask' for admin rights if the
user has them.  Using powershell makes the pop up blue instead of orange
and states that the company is Microsoft, it also doesn't drop an exe
on the system.  Looks like 32 bit https works but if you migrate out you
loose priv and if you run cachedump the session hangs.
Updated with comments from jlee-r7 and Meatballs1

Added fail_with instead of just print_error
figured a way to execute the cmd_psh_payload with out using gsub
added case statment for datastore['TECHNIQUE']
Added check method

The method checks to see if the user is a part of the admin group.  If
the user is the exploit continues, if not the exploit stops because it
will prompt the user for a password instead of just clicking ok.
Added priv lib and runas lib

Cleaned up code with using the new lib files
Dont check for admin
Tidy up
Merge remote-tracking branch 'upstream/master' into land_2551

Conflicts:
	modules/exploits/windows/local/ask.rb
Tidy up
Merge pull request #1 from Meatballs1/land_2551

Some changes and cleanup.
Merge remote-tracking branch 'upstream/master' into land_2551
Quick rubocop
Fix for newer powershell
Fix var name
Land #2551, Runas post library and powershell ask technique