Related to #15758
Changes:
- Updated the copyright year in email templates to be set to the current
year when the email is sent.
Testing steps:
1. Configure a local Fleet instance to send emails to Mailpit
2. Activate SMTP to send a test email.
3. Invite a new user to the Fleet instance.
4. Change the email address of a user.
5. Log out of the Fleet instance and send a password reset email.
6. Go to the Mailpit dashboard and look at the copyright years in the
emails sent by the Fleet instance
Previously a Go package attempting to import Fleet packages would run
into an error like "server/kolide/emails.go:93:23: undefined: Asset".
This commit refactors bindata asset handling to allow importing Fleet as
a library without changing the typical developer experience.
