python/skytools update

python/skytools update

- docstrings
- some preliminary python 3.0 compat (var names, print())
- sync with 2.1-stable

adminscript:
- move exec_cmd function to dbscript

dbstruct:
- support sequnces.  SERIAL columns are not automatically created,
  but the link beteween column and sequence is.

psycopgwrapper:
- drop support for psycopg1
- beginnings of quick DB-API / DictRow description.

quoting:
- new unquote_fqident() function, reverse of quote_fqident()
- quote_statement() accepts both row and dict

dbscript:
- catch startup errors
- use log.exception for exceptions, will result in nicer logs

sqltools:
- exists_sequence()

_pyquoting:
- fix typo in variable name