Ability to clear all overrides (Latched in particular)

[slominskir]

We likely need the ability (likely in set_override.py) to clear all overrides. Perhaps allow targeting a specific type of override (like Latched). What I'm observing is chatty alarms (or perhaps during commissioning temporarily INVALID alarms) appear to quickly result in thousands of Latched overrides. Until we define the correct ondelays or otherwise correct the nuisance alarms we've got a lot of latch records to acknowledge one-by-one.

Related: Should already disabled alarms latch? Or perhaps if you re-enable an alarm latches are automatically cleared?

[slominskir]

Note: most of the alarms that are latching are likely supposed to be filtered out. See: #24

However, bulk operations may still be useful. See: JeffersonLab/jaws-admin-gui#36