A big rearrangement.

A big rearrangement.
* Moved class functions around so that they appear in the first database
version that supports them.  Lots of stuff moved to BaseDB and Postgres
* More support for new 7.3 features
* Known bug in schema support at the moment - I'm working on it
* Looked at Raymond's sequence stuff, did a few things:
 - Moved the getSequences function to Postgres instead of Postgres71 since
   sequences are found in all versions of postgres
 - Added a comment for the function
 - Added support for showing system sequences or not
 - Used like instead of regexp, just looks nicer
 - Fixed missing /table tag that was causing display probs
 - Note: I think the code layout in sequences.php probably should be
   made to match that of the rest of the codebase (coding standards???)
 - Obviously it's an early cut, but it's going in the right direction
* Added support for deleting rows when browsing, using a function that
  finds a unique identifying get for tables.
* Edit row next