[pm] callback chain for adding thinclients

The addNewThinClient() functions has been modified to use callback
chain for storing thin client objects.

ssh command has been changed by using full path

getDCHPClient() and getTouple has been refactored to remove using a
temporary file to read output from lease parser. It now uses
getProcessOutput() to pass around the ip/mac address touple.

adding debug logs as well
[pm] new MAXCLIENTS parameter on config
[pm] TestMode and MaxClients

cleaned code by removing previously commented-out code

added TESTMODE for testing PoENotification
EvaluatePoENotif() now uses now uses MAXCLIENTS to determine if
initialisation of ThinCliens has been finished

powerUpPoE(port) is now used after adding the ThinClient to the list

edited debug messages for helping on diagnosing errors.
[pm] leading new line on echo lines
[pm] using 're' module instead of 'parse

parser has been refactored to us the built-in ‘re’ module instead of
the ‘parse’ module, which needs to be installed to python system for it
to work. (using pip or easy_install)

This reduces further changes on the Mgmt VM