First commit of a simplified calculator module: the Sidereal time module. The major change is that there's no "Compute" or "Clear" buttons anymore; changing any of the data fields automatically updates the output data field. In the case of this module, you can actually modify either the Local time or Sidereal time, and it will adjust the other one to match.

Other changes:

+ using Local time instead of UT (it was always Local sidereal time, so it makes more sense to use LT).

+ Instead of entering a longitude, the user specifies a geographic location from our database.

TODO: I haven't modified the Batch mode yet; I will probably change the
Interactive modes first, then tackle the Batch modes.

Is anyone interested in helping to simplify the remaining calculator modules?