CBQE-1573: new plotter.py to generate html charts

in the process of completely replacing plotter.py
with this new implementation that uses python pandas
for managaning timeseries data created by cbmonitor
and pygal for html charting.

to run:
* launch a system test and wait for it to complete. then,
* python tools/plotter2.py <bucket1>,<bucket2>

creates subfolders based on testname with perphase and pertest charts


REQUIRES-  pip install openpyxl pygal pandas

Change-Id: I6b8de2b38ac0c2ee3b353a71c5f2b8f39e9eb604
Reviewed-on: http://review.couchbase.org/29828
Tested-by: Tommie McAfee <tommie@couchbase.com>
Reviewed-by: Tommie McAfee <tommie@couchbase.com>