Merged "with_ruby192": Complete Ruby 1.9.2 and PostgreSQL support

[Igal Koshevoy]

I've been running the "with_ruby192" branch on calagator.org for a
week. It works great. I've merged it into "master" and deleted the
obsoleted branch.

The branch adds full support for Ruby 1.9.2p180 and p290, while still
supporting 1.8.7. Most of the work needed was to deal with changes to
libraries. Ruby 1.9.2 can't run Hpricot, so I had to port our old
version of Mofo to Nokogiri because there are no working libraries for
parsing hCalendar for Ruby. I also had to upgrade a bunch of libraries
because 1.9.2 ships a broken YAML parser, with different bugs in p180
and p290, so I had to avoid using YAML and replace it JSON in some of
our code and libraries.

The branch adds full support for PostgreSQL, while still supporting
Sqlite3. If you're writing or modifying raw SQL, then you should do
this with PostgreSQL because its so much more exacting about what code
it'll accept, and these resulting queries will usually run fine in
Sqlite3. In contrast, Sqlite3 is very forgiving and cheerfully accepts
logically absurd queries and manages to produce sensible results, and
these won't run in PostgreSQL and are a pain to port.

-igal