Fixed Swiss Ephemeris version number

It's actually 1.76, although the sources suggest it's 1.75
Went to major version 2.0

There are too many API (and ABI) changes there, so let's just switch to 2.0
Made GsweSignInfo a refcounted boxed type
Typo fix in house system name, in gswe-types.h
Added code samples to use with GObject Introspection

* JavaScript
* Python
* LUA
* Perl
Moved all GError domains into one global GSWE_ERROR domain
Made GsweAntiscionAxisInfo a refcounted boxed type