[Build] prepare new development version 0.7.1-SNAPSHOT

Change-Id: I03814a9cb5b60b5b5490d52e905923509070d034
[Java] fix synchronization bug in proxy invocation handler

access to connector status and queued requests was not properly
synchronized

Change-Id: I9214c53fdb6d24354b9209d5fca43fdc1ff5a870
[Release] prepare release 0.7.1

Change-Id: I3292692d8ff4ecabfb9bb3cea33cb62de844dc0a
[Build] prepare new development version 0.7.2-SNAPSHOT

Change-Id: Ida912c7f217b78ede34c0978df1313c20b967b62
[C++] replies of void methods contain null response

* up to now replies of void methods are serialized in C++ as
  "response":"void"
* Java expects replies of void methods to contain no
  response or null response in JSON
  "response":null
* this was already fixed in SVN commit 4095 but didn't make
  it into GIT for unknown reasons

Change-Id: I5172e567d9bf5c7be69abf1d8d57e526f729823c