Add note field to Account/Domain and CLI

Modify SQL to add note field to domain_data and users

man: vmm.1: subcommand's name argument is optional now. Based on martin f. krafft's v2 of changeset c340ba4bd544.

Allow username to take no argument to erase value Once a username has been set, it could not be removed via the UI. Now, if no argument is passed to username, the value stored is replaced with NULL.

Add inheritance as a feature to README

Change 'force' argument to reset user records for tid/ssid/qid If domain{quotalimit,transport,serviceset} are run with 'force' and settings are inheritable from the domain, then rather than to copy the ID to the user table, the affected field in the user records should be set to NULL so that the domain default is used.

Change UI to accept 'default' to restore inherited values Instead of explicit values for tid/ssid/qid, the UI now accepts 'default', which removed user-pecific settings and hence causes domain defaults to be used.

Modify userinfo output to indicate when domain defaults are displayed When Account instances reference NULL tid/qid/ssid, the data must come from the associated domain, and this should be indicated. For transport and services, this is easy to do as the string passed in the info dict can simply be modified. For quotalimit, however, another method must be used due to the CLI-side formatting. All approaches use a common formatter outsourced to the common.py file.

Modify Account class to handle NULL references This patch modifies the Account class to defer to using the associated domain's tid/ssid/qid fields if the per-instance fields are None/NULL.

Modify SQL update script to accept NULL fields for users The value NULL in the qid/ssid/tid fields of the user table means that the value from the associated domain record should be used instead. This patch modifies the PL/pgSQL functions used by Dovecot and Postfix accordingly.