mysql_user and mysql_db both take a login_unix_socket option.

This patch adds docs that describe how to use it.

The target parameter is not required, the DOCUMENTATION section was in error.

According to the MySQL docs[0] the password should be stored after
'password=' instead of 'pass='.

[0] http://dev.mysql.com/doc/refman/5.1/en/password-security-user.html

Fixes #1848.

 - added terse syntax to modules.rst
 - added description of special variables to template module

mysql_db: use the database to test connexion, added dump and import state - requires target=path/to/a/file

Add encoding lines to python modules such that they can take unicode options if they are fed them, since the
AnsibleModule stuff no longer base64 encodes for simplicity and speed reasons.

mysql_db: added 'encoding' and 'collation' args
postgresql_db: added 'owner', 'template' and 'encoding' args

Changing the parameter names to be consistent, and adding root user default with empty password, as per mysql standard

Check file exists instead of relying on the exception. Leave the exception catch in, in case the file is deleted or some other issue crops up

Changing to read from a file pointer instead so that an exception is thrown if the file doesn't exist