Previously, you could log into an account named "MyAccount" by entering
either "myaccount" or "MYACCOUNT" (or any other case conbination).  This
patch requires logins to succeed with case-sensitive usernames.

I have also decided, that I wish to disallow duplicate usernames if the
only difference between them is case.  There can only be _ONE_
"myaccount" (of any case combination), even if he's known canonically as
"MyAccount".  This particular functionality is not changed by this
patch.  I'm just noting it as a deliberate decision not to change, by
policy.

Note that _passwords_ always have been, and still are, case-sensitive.
They are salted and hashed before they even hit the database.

Signed-off-by: Malf Furious <m@lfurio.us>

This function helps further abstract agents.  We want to get all users
belonging to a pad that is owned by a group, or more specifically - an
agent.  If this agent is a user, that user is our only user to collect.
If this agent is a group, we want to capture _it's_ owner along with all
of it's members.

Signed-off-by: Malf Furious <m@lfurio.us>

Previously, these functions would always call session_start() before
doing most of their work.  However, I've found that calling that
function two or more times within the lifetime of a program results in
NOTICE messages output from the PHP interpreter.  Therefore, I am now
only calling session_start() if the session is not already active.

If the session is set to an invalid (eg:  deleted) user GUID, an
exception is (correctly) thrown.  This commit catches that and enables
getCurrent() to close the bad session and return NULL.

Now setting the name for email FROM field using system config
'smtpFrom'.

Added calls to function saveObj() where $this is mutated.

Lookup all groups a user owns or is a member of.

Added the function to verify and update the user's password.  Added the
function to confirm and update the user's email address.