Twitter markers "not showed" bug fixed, with Twitter4j client integration.

This branch fix the problem related to the new twitter API search, now available only with oAuth protocol.
A Twitter4J client is now added to Mixare project (with oAuth support integrated), that can now search and show correctly georeferenced tweets. Also JSON data manager has been update for this patch.

More info on the bug reported (and fixed in this branch) available here: 
http://code.google.com/p/mixare/issues/detail?id=157&colspec=ID%20Type%20Status%20Priority%20Stars%20Version%20Owner%20Summary.
 
A simple screenshot showing now the tweets on the user screen is attached here:

![screenshot_2013-10-18-17-51-37](https://f.cloud.github.com/assets/5201918/1446832/533814dc-423e-11e3-9d40-c12765c4c7a6.jpg)