Basic Google Analytics Measurement Performance support.  Notes about how this works:
-no statistics are reported if a .h2o_no_collect file is in the run directory or ~/
-all nodes report cloud size and hadoop version as a Startup system info event at node boot
-this uses the same filtration of REST requests as maybeLogRequest (job polling and such are ignored)
-the user agent for REST request is the Java and OS version of the H2O node
-each REST request stores the client (R or web browser) user agent as custom dimension 1 (cd1)
-R code has been modified to report R version
-this does suck in the library https://github.com/brsanthu/google-analytics-java
--the library needed to be changed to drop slf4j and to back port it to use Apache http-client 4.1 (instead of 4.3)
--app view hits (no longer in GAMP) are now screen view hits
--removed the automatic creation of a unique UUID for every run (instead UUID is based on UID and MAC)
--useragent is now automatically set and sent by default
Gets hadoop version for reporting at startup.  Allows Hadoop mapper to opt out all jobs (via .h2o_no_collect file).  Allow h2o node startup to opt out via command-line.
Only one node reports the cloud size and hadoop version now.
Fixes Hadoop opt out and single report of cloud size.
Merge branch 'brandon-ga'