fixup error msg for when libdbus is not available
switch dbus log to log channel 'desktop'
fix a bug with the chat synposis generated by dbus notifications

When searching for the next line, if it didn't find one, index
npos would cause it to wrap around unexpectedly.
fixup notifications records data structure

Changed it from a list, which would be sequentially searched by id
and owner, to a multi_index container using hashed indices for both
of these fields.
fixup to dbus notifications: only chat msgs have history synopsis