Add local override of DataTreeDialog. [1542]

I want to work out any GUI kinks before submitting to Unidata.
Add DataTree search to formula param dialog.

This takes the DataTree searching functionality from DataSelector and
generalizes it into the “DataTreeSearcher” class. Each DataTree in the
formula dialog currently has its own DataTreeSearcher.

The basic searching functionality is pretty much working as
expected…provided you limit your interaction with the search/cancel
buttons to mouse clicks. There’s *apparently* an issue with the
keyboard focus that causes the “DataTreeSearchers” to stop responding
to the “control + f” or “cmd + f” hotkeys. :(

Also…apologies for not being able to get this out before the dev
meeting ended! :disappointed:

[1542]
loadFile:  Fix for 2D case of _MappedGeoGridFlatField binary override -
leverage "make2DGridFromSlice" functionality in GridMath when needed.

Note, for now this only fixes the "a-b" syntax, not the "sub(a, b)"
syntax.  If this fix passes testing, overriding sub, add, etc. to take
advantage of this fix should be straightforward.

[1589]
[0] Dreamweaver updates synced from web server.
[0] Dreamweaver updates synced from web server.