Dont rescue Exception
Check for a valid handle

If service already exists open a handle.
If we have a valid handle ensure we try and close it.
Allow passing of servicename etc
Allow servicename/displayname to be set

Tidyup psexec some more
Use error codes to give more feedback
Remove service
Catch file not found
Merge branch 'master' into psexec_refactor_round2

Conflicts:
	lib/msf/core/exploit/smb/psexec.rb
	modules/exploits/windows/smb/psexec.rb
Refactor to new psexec style
Pull in @jtesta's DCERPC Services work
Fixup open sm
Use dcerpc_services
Get it all working...
Handle existing service names
Handle request timeout
Moar constants
Auto persist
Catch ACCESS_DENIED
Aux doesn't have rand_text_alpha
Refactors

Add a Rex::Constants::Windows module to hold windows constants
Convert DCERPC_SERVICES to a class and move to Rex