NSW Simulation - sTGC pad trigger changes for athenaMT

Changes in the sTGC pad code for the migration to athenaMT. More specifically:

• Simplified algorithm workflow: made pad cache local (potentially fixing segmentation faults when running in MT mode) and removed enum structure as not needed anymore after the previous change
• All previous declareProperty instances replaced by Gaudi::Property ones, in order to change them from the main steering python, if needed
• Removed deprecated syntax
• Declared functions as const when possible
• Moved include declarations to header file and removed duplicates
• Clean-up of variables/functions/comments not used or not useful to understand the code
• Improved code readability: fixed alignment and indentations, expanded tabs->spaces

Finally, the MMTriggerTool.cxx and MMLoadVariables.cxx files were changed to expand tabs->spaces only

./cc-ing @iodice @rosati @vadamico @ztarem