New release of Orafce extension

I released new mostly release of Orafce. Today it is massive package of emulation often used Oracle's API and the emulation is on maximum what is possible.

Now Orafce has good and very nice documentation written by Horikawa Tomohiro (big thanks for his work).

There are not too much news for people who use Oracle 3.6:

• possibility to better emulate || operator for varchar2 and nvarchar2 types
• few bugfixes
• only PostgreSQL 9.4 and newer are supported
• support for PostgreSQL 11, current master branch (future PostgreSQL 12) is supported too