Refs #8906 - More descriptive names for monitor workspaces.

Essentially, the name of the original workspace name with a "_monitors"
suffix.
Refs #8906 - Move get_monitor method to Sample class.
Refs #8906 - SliceEvent now gets monitor from Sample class.
Refs #8906 - Cleaner way to load monitors for event files.
Merge branch 'feature/8906_improve_monitor_handling_in_isis_sans' into develop