Move mod-sequence mailbox availablity checks into base class
[mms] Only do UNCHANGEDSINCE check when storing flags if the user explicitly passes the 'unchangedsince' parameter.
Update phpdoc
[mms] Add properties to Sync object to allow retrieval of previous sync state status.

Conflicts:
	framework/Imap_Client/package.xml
Fix exception name
In 6.0, this is just a regular exception
Merge branch 'master' into imp_6_1

Conflicts:
	framework/Imap_Client/package.xml
	imp/lib/Ajax/Application/ListMessages.php