Use "E-mail Templates" term in codebase instead of "E-mail Events"

1. In-Portal has "E-mail Templates" section, where all e-mail templates are defined.
Later via special function call developer can render each of templates and send result to e-mail address given.

But internally we call them as "e-mail events". I think we should do some renaming to have "e-mail templates" term across the system.

2. We also validate, during e-mail sending, that supplied e-mail event name has only upper case letters and dots, but we don't validate the same upon e-mail event adding/editing.

This way it's possible to enter e-mail event name, that won't be sent just because it's named incorrectly.