Set SQLite page size to 4K: Closes #7423

This speeds up startup time immensely, probably due it matching the
the filesystem's or Linux memory mgmt's page size.  It's also
expected that this will improve database performance in other ways,
as the default was 1K, meaning potentially more I/O than necessary
for standard operations.

sql/version-014.sql

@@ -0,0 +1,4 @@
+--
+-- Dummy file to upgrade to version 14.  See imap-db-database.vala for the
+-- actual code that gets executed here.
+--