Trim down the default attributes that came with area detector ...

[prjemian]

@qzhang234 writes by email:

... Cam and CamBase classes so that they cover only the ABSOLUTE MINIMUM of attributes, such as acquire, file name, exposure time, etc. Adding attributes are far easier than blocking attributes and allows end-users to take responsibility/ownership for their decisions. In addition, unnecessary attributes lead to unexpected crashes; it is much easier to debug a class that is missing one necessary attribute that a user needs, than a class that has too many unnecessary attributes that is irrelevant to the use case of interest (e.g. Grasshopper rgb correction value for a Pilatus).

[prjemian]

See BCDA-APS/bdp_controls#38 for a set of goals.