REL-2072, OCSADV-29: updates to guiding controls

These changes are mostly about REL-2072, making the guiding controls appear for ToO observations.  There is some overlap there with OCSADV-29 which requests that the guiding controls appear for empty sequence observations.  Both these situations were filtering out the guiding controls because the observation isn't considered to *need* a guide star.  This update makes the manual guide star search button always available and the AGS controls and labels available whenever it is possible to do an AGS lookup.  Guiding feedback is still withheld unless the observation actually needs a guide star but the definition of "needs a guide star" has been adjusted for ToO observations to mean that a non-default target is available.

The first of Bryan's requests in OCSADV-29 is covered by these changes:

* The AGS buttons should always be displayed instead of only appearing when an observe is present in the sequence

In addition, the next two requests were incorporated as well since they are trivial label updates.

* The Plot... button should be labeled "Manual GS" since this button brings up the Manual Guidestar search dialog
* The Update/Search button should be labeled "Auto GS" to better distinguish the functionality from the manual search