Remove mention of Oryx and commercial support which no longer exists.

Remove mention of dual license situation which has not been true since
3.1.3.

Update name of license to be "PostgreSQL License". As of 2010 it is an
official OSI approved license.

Edit bsd.txt license to remove mention of Oryx. Licenses -- even open
source licenses -- mentioning nonexistant companies is controversial.

Finally, rename bsd.txt to license.txt.

Arnt, Ahbijit -- I'm not trying to step on your toes, just wanted to
clarify the documentation to make it more accurate. Feel free to reject
this pull request. If rejected, I will wipe out my current fork. I would
never attempt to maliciously relicense/redistribute your software.