Add psql_tid and psql_pid

Adding PostgreSQL transaction ID
and PostgreSQL backend PID to WSCursor and logs
Adding feature to list all active wscursors
Add kill WSCursor
cursor -> sync_cursor
Fix type last_access
Merge pull request #5 from gisce/gh5

WSCursor API
Merge pull request #4 from gisce/gh4

Assign transaction_id and pid to WsCursor
Merge pull request #6 from gisce/developer

Developer