Implement automatic alignment star selection using fixed long/lat/time

[caseyfw]

Currently alignment stars are hard coded - this needs to change.

Good alignment stars can be automatically selected using the following method:

1. Get the telescope's current long/lat/time - using GPS module?
2. From a list of the 50 brightest stars (name, magnitude, RA, Dec in EEPROM?), determine which are above +20° declination.
3. Pick the brightest two.