Add a test that dumps trigger menu

It would be useful to be able to print the trigger menu and pipe it through grep etc, especially if the operation didn't take several minutes.

This adds a script (test_menu_dump.py) that does that in a second or so (the -n option). In the meantime @cpollard said having this script would be useful, so I might as well check it in.

At @khoo's suggestion I also added an option (-p) to run the chain parsing and get a the chain dictionary. This seems to work in all but a few chains in the physics menu. The exceptions are:

HLT_e5_lhvloose_bBeeM6000_L1BKeePrimaryn
HLT_2e5_lhvloose_bBeeM6000_L1BKeePrimary
HLT_e5_lhvloose_bBeeM6000_L1BKeePrescaled
HLT_2e5_lhvloose_bBeeM6000_L1BKeePrescaled

which seem to need access to the input file to parse properly.

I also added a unit test that runs with the -p option. I'm going to propose leaving it at this for now, since having a quick way to run the chain parsing is something a few people thought sounded useful.