Rebrand to INBUXA: product name, protocol greetings, sign-in page, calendar templates, logos, README

One branding module (types::brand!) supplies the name to every protocol
greeting, the HTTP realm, the startup banner, Received headers, the
user agent, the IMAP ID response and calendar PRODIDs. The sign-in and
calendar pages take ihasmail's palette and font and the INBUXA logo, and
calendar emails embed the INBUXA lockup. Default calendar and address book
names follow. Protocol identifiers (urn:stalwart:jmap, vnd.stalwart Sieve
extensions) and upstream copyright notices are unchanged.

tests/resources/itip/google_calendar.txt

@@ -61,7 +61,7 @@ summary.rrule: Rrule(ICalendarRecurrenceRule { freq: Weekly, until: None, count:
 summary.summary: Text("Meet me maybe")
 BEGIN:VCALENDAR
 METHOD:REQUEST
-PRODID:-//Stalwart Labs LLC//Stalwart Server//EN
+PRODID:-//INBUXA//INBUXA Server//EN
 VERSION:2.0
 BEGIN:VEVENT
 X-MICROSOFT-CDO-OWNERAPPTID:299828133
@@ -176,7 +176,7 @@ summary.summary: Text("Meet me maybe")
 ~summary.description: Text("This is the event description")
 BEGIN:VCALENDAR
 METHOD:REQUEST
-PRODID:-//Stalwart Labs LLC//Stalwart Server//EN
+PRODID:-//INBUXA//INBUXA Server//EN
 VERSION:2.0
 BEGIN:VEVENT
 X-MICROSOFT-CDO-OWNERAPPTID:299828133
@@ -224,7 +224,7 @@ END:VCALENDAR
 # Make sure the original alarms are preserved
 > get [email protected] [email protected]
 BEGIN:VCALENDAR
-PRODID:-//Stalwart Labs LLC//Stalwart Server//EN
+PRODID:-//INBUXA//INBUXA Server//EN
 VERSION:2.0
 BEGIN:VEVENT
 X-MICROSOFT-CDO-OWNERAPPTID:299828133