<feature>SQL package also connects to a PostgreSQL database server</feature> <feature>SQL package: added cacheResults parameter to SQLSource</feature> <feature>SQL package also handles connection timeouts</feature>
<feature>SQL package also connects to a PostgreSQL database server</feature>
<feature>SQL package: added cacheResults parameter to SQLSource</feature>
<feature>SQL package also handles connection timeouts</feature>

Added support to connecting to a postgresql using psycopg2 python package (which is based on python's db api 2 and postgres' libpg*.

This is for connecting to the CMOP database

 vistrails/packages/sql/__init__.py
   - using py_import to import db libs
   - class DBConnection:
      new methods:
       get_db_lib()
        depending on the protocol set, returns the corresponding lib
       open()
       ping()

   - class SQLSource:
      new input cacheResults
      new methods:
        cachedOn
        cachedOff

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