Update Templates & Reminders to use proper salutation.

About a year ago, major email providers like Apple and Microsoft implemented to SPAM checks that look for a proper salutation. If the name on the mailbox isn't referenced in the communication, it considers it an email blast and scores the email bulk/spam.

To improve email deliverability:
Change the default #client to Hi $contact.first_name,

End users should be encouraged by documentation to set a signature that includes their name, though this is optional.

For example,

Thank you,
FirstName LastName