TrigT1CaloMonitoring+xAODTrigger: Protect against bad efex iPhi

An efex in STF has a shelf number of 12, which leads to an out-of-range iPhi. This was happening in the test_bulkProcessing_splashes ART test. If the job is run in a debug build, this was triggering an exception in TAxis because we try to fill an out-of-range bin. Protect.

Also add references to the documents describing the EFex data format. Note that the shelf number can be 12 for the test facility (and that iPhi will be out of range in this case).