Account activation email template

* Implemented the email template for activating newly created
accounts.

* Use URIBuilder to build the URL which the recipient of the email
shall be asked to click
Password reset email template
%token% placeholder in CrowdmapID mail body

* Added missing %token% placeholder to the email body for
CrowdmapID password reset requests. CrowdmapID replaces
this placeholder with the password reset token.

* Removed the email template for CrowdmapID password reset
requests