counters: extend measurement and counter interface
Extend the measurement and counter capabilities.
Most important changes are in measurement.
The idea is just to improve a little the counter interface so it becomes more useful for
ID31: reflectometry continuous scan
milestone. Probably this will require another major refactor once the continuous scan evolves.
Details:
- change counter API from: read(acq_time=None) to: read() count(time=None, Measurement=None)
- add Measurement capabilities: sum, single and full measurement, timestamp
- default count: measure and return average
- apply changes to existing counters
- apply changes to existing procedures (scans)
- add unit tests