pgcli/TODO

* [ ] Deal with commands that have no return rows (such as delete, begin transaction etc).
* [ ] Add a lot more SQL keywords to auto-completion (Read the postgres docs)
* [ ] Detect a '.' and parse the word before it and get it's real name.
* [ ] Add more complex slash commands such as \d <table_name>.
* [x] Control smart completion via config file.
* [x] Figure out how to deal with transactions.
* [X] Add a config file.
* [X] Add context sensitive auto-completion.
    * Check how sqlpython is doing it.
* [X] Prettify the output into nice columnar tables.
* [X] Check how to deal with failed commands that result in dangling transaction.
* [X] Add a history file.
* [X] Deal with errors that happen at connection (password, host etc).
* [X] Deal with errors that happen during sql execution.
* [X] Add auto-completion based on the tables, columns names.
    * launch psql with -E option and try \d, \dt etc and copy the sql statements.
* [X] Translate the commands to pg backend.
* [X] Add options to read the host, user, passwd etc.
* [X] Add the back-slash commands.
    * launch psql with -E option and try \d, \dt etc and copy the sql statements.