Inconsistent location of messge footer/header files #507
Fixes: - Message footer/header files of domain/site default are put in `mail_tt2` subdirectories while those of list config are not. Fixed by put all of them in consistent location without intermediate directories (See also Notes below). - Entries for header/footer files in `edit_list.conf` were ignored. Changes: - File names themselves of header/footer were changed: `message_header`, `message_header.mime` etc. This is due to concideration about conflict between files and directories with domain names (See also Notes below). - Header/footer files with `.mime` extension: Previously, files with this extension were always preferred, then files without extension were used. This behavior has not been documented. Now files with extension will be searched only in case `footer_type` is `mime`. Files without extension will be searched in both cases. Notes: - Files with older names/paths in list/domain/site config directories will be copied to new location during upgrading process. - Template files with old names in families (`message.header.tt2` etc.) will be used as before and will be copied to new location during instantiation. If files with new names (`message_header.tt2` etc.) will be preferred, if they will be added. Known bug: - There are no web UI to edit global footer (`message_global_footer`).