Add a helper function to identify BMG chambers

BMG chambers use a different digitization chip from other MDTs, including the BMEs, which leads to different behaviors, so it's useful to have a function for identifying BMG chambers alone.

Adding @diehl

This merge request affects 1 package:

• MuonSpectrometer/MuonIdHelpers

Adding @rosati ,@wleight as watchers

added MuonSpectrometer master review-pending-level-1 labels

CI Result SUCCESS

	Athena	AthSimulation
externals
cmake
make
required tests
optional tests

Full details available at NICOS MR-20941-2019-02-06-20-48
Athena: number of compilation errors 0, warnings 3
AthSimulation: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST 33446]

The changes look ok. Adding review-approved label.

L1 shifter

added review-approved label and removed review-pending-level-1 label

merged

mentioned in commit 7d4d38aa

added sweep:ignore label