organize common terms by instrument mode

[prjemian]

The 9-ID-C instrument is configured for different modes (USAXS, SAXS, WAXS, SBUSAXS, Radiography, Imaging, ...)

Each mode has a set of variables needed by the local scripting tool. These variables are stored in EPICS so other tools can access/use them.

Build a scalable ophyd structure with future expansion in mind, attempting to avoid chaotic growth.

mode	DX0	DY0	AY0	...
USAXS	__	__	__	__
SBUSAXS	__	__	__	__
SAXS	__	__	__	__
WAXS	__	__	__	__
Radiography	__	__	__	__
Imaging	__	__	__	__
...	__	__	__	__

some terms are common to more than one mode, some common to all

[prjemian]

related to #36

[prjemian]

@jilavsky
in local/usaxs_commands.mac

these two use the same PV

def WAXS_AcquireTime 'epics_get("9idcLAX:USAXS_WAXS:AcquireTime")'
def WAXS_EXP_TIME 'epics_get("9idcLAX:USAXS_WAXS:AcquireTime")'

the CAM1 screen labels it as Exposure Time but the PV is AcquireTime

or did you want ExposureTime?