Lp 1801163: Switch to Email::MIME in SendEmail A/T Reactor

Lp 1801163: Switch to Email::MIME in SendEmail A/T Reactor

Switch from Email::Simple to Email::MIME Perl module in the SendEmail
Action/Trigger Reactor.  Email::MIME properly encodes unescaped header
fields when added to the message with the header_str_set method.

We allow only 1 of each address field to be created while doing the
encoding, so that messages conform to RFC 2822.

This commit adds a new prerequisite as mentioned in the release notes,
so be sure to install the prerequisites for your Linux distribution
before installing.

You can test this with concerto data from a fresh installation by:

1. Configuring your test system to send email.

2. Updating all actor.usr entries to have your email address.

3. Updating the New User Created Welcome Notice event definiton to
   active = true.

4. Run the action_trigger_runner with --process-hooks --run-pending.

5. You should get 237 new user welcome emails.  The exact number is
   subject to change.

Signed-off-by: Jason Stephenson <jason@sigio.com>