Using RX Java for Summariser (and possibly other places)

[UBIK LOAD PACK Support]

Hello,
It might be interesting to look into using this library to better manager
listeners like Summariser and even all GUI related listeners related to
Bugzilla 60687  (see SwingScheduler.instance() in Readme):

   - http://www.vogella.com/tutorials/RxJava/article.html
   - https://github.com/ReactiveX/RxJava


Regards