Include many methods to set the RA/Dec of a SkyPoint to increase programming clarity

Review Request #106658 - Created Sept. 30, 2012 and updated

Akarsh Simha
khudyakov, kulaga
To reduce confusion and increase clarity, define three new coordinate-setting methods for SkyPoint, and modify the existing one so that it has a mandatory epoch argument.

Earlier, there was only one method called set(RA, Dec) that would set both (RA0, Dec0) and (RA, Dec). This must be handled with care. Instead, the new methods set only the valid data, and invalidate the other data. This might not be very useful in itself, but the clarity it adds is useful. Just a plain "set" needs an additional epoch argument, and uses deprecess() to set the RA0 and Dec0 correctly. The explicitness in using setCurrent, setJ2000 or setBoth is advantageous.
A basic run of KStars rendered the SkyMap seemingly fine. The use of slotDSS() gave correct results for September 2012.