Added backup, swap and tags files to .gitignore

Conflicts:
	.gitignore
Added translation-related lines to .gitignore
Added SWE-Glib sources, which currently wraps Swiss Ephemeris function calls
Changed signal name GsweMoment::moment-changed to changed
Removed unnecessary julian_timestamp property of GsweMomentPrivate
Changed GsweMoment.timestamp from GDateTime to GsweTimestamp
Added GswePlanetInfo.sweph_id for Swiss Ephemeris planet IDs
Added aspects and house systems to gswe-types.h
Removed unneeded global variable from SWE-GLib
Added Swiss Ephemeris planet IDs to planet info table initialization
Made planet_info_table externally accessible
Added house systems to library initialization
Modified GsweTimestamp so the time zone must be specified as a double (in hours)
Outsourced house cusp position calculations to SWE-GLib.
Moved the GsweHouseSystem typedef up in gswe-types.h to create some consistency
Added planet point values to SWE-GLib's gswe_planet_info_table
Created gswe_sign_info_table
Added some documentation
Added GswePlanetInfo.real_body field

It shows if the given astrological body's position can be calculated with
Swiss Ephemeris' swe_calc() function.
Created planetary calculation functionality