mail/rainloop: Update to 1.17.0

Since only one edition "legacy" is provided under MIT license now,

• Remove mail/rainloop-community port and add entry to MOVED and UPDATING.
• Use '=' rather than '?=' for PKGNAMESUFFIX and COMMENT.
• Update license information.
• Remove patch-rainloop_v_1.16.0_app_libraries_MailSo_Base_HtmlUtils.php that is included in upstream.