Make max and min search periods configurable.
Created by: willrogers
The default max search period for the channel access client in EPICS base is 300 seconds, and it honours the environment variable EPICS_CA_MAX_SEARCH_PERIOD. The default for JCA is 30 seconds. This commit makes that value (and the equivalent min value) configurable either using the environment variable or the jca properties file.
See #25 (closed) - very happy to discuss this if you would like changes.