Add Sequences for all Primary Keys

This is an update from Bruce Sun, to enable the creation of unique
integer primary keys from multiple simultaneous users.  Bruce writes
these comments:
* I added the sequence for the primary key in each table.
* In dbWrench, sequences are displayed in the interface. You need to go
to Edit->Preference->Database Explorer to enable "Showing Sequence
Folder".
* I used this way to name the seqence: table_name + "_id_seq", e.g.
Annotations_id_seq.