lower messaging's min-large-message-size value in standalone-full.xml

AS7's messaging subsystem defines 2 attributes:
journal-file-size => 10MiB
min-large-message-size => 100KiB

However, for startup performance issue, the standalone-full.xml sets the journal-file-size at 1OOKiB. This leads to issues since it's the same value than the min-large-message-size.
If we want to keep a low journal-file-size value in standalone-full.xml, the min-large-message-size must also bet set appropriately (eg 75KiB?)

For production use, however, we should suggest to the users to remove the journal-file-size and min-large-message-size from standalone-full.xml to use the default values (resp. 10MiB & 100KiB)