Adds doc string to query validate functions in V2 API

Rename is_timestamp_valid parameter to allow_timestamps and add
doc string to _validate_query and _validate_timestamp_fields
functions, related to the bugfix of bug 1280975.

Change-Id: I7c8564ce88d048e5b7d6d1e3c7109c5cb08e48f3
Rename id to alarm_id of Alarm in SqlAlchemy

This change makes the schema more consistent.

It also fixes a bug preventig querying alarm_id
on /v2/query/alarms API.

Closes-Bug: #1282667

Change-Id: Id4d67fa5ee679fe1c8d86b8575a99bfb89e384fa
Merge "Adds doc string to query validate functions in V2 API"