nunaliit2-couch-client: Add CouchDbChangeMonitor to make servlets that
monitor the database more responsive and more efficient in the use of
network connections.

nunaliit2-couch-date, nunaliit2-couch-onUpload,
nunaliit2-couch-submission, nunaliit2-couch-user: Take advantage to
CouchDbChangeListener interface to be notified of changes to the
database.

Issue #244