Darwin: added network response checks to all curl and git calls. Also added --connect-timeout 30 to curl http calls

Darwin: reworked the python3 verification to be more accurate with apples default install of python 2.7.x

CI system is having trouble here and it's possible others will as well. For some reason (failed previous builds) the mongo-cxx-driver temp dir is sticking around and causing problems since git clone will not stomp on it

It seems like the mongo-c-driver will elected to take a shared lib of libbson over rebuilding it as a static library. This yields a build error later on as the mongo-cxx libs can't find a static libbson. So enforce building of libbson internal to the mongo-c-driver build

Nearly all other libraries we link to is via static linkage (boost, k1 lib, llvm/clang, etc) so this one should follow suit. Otherwise users would still need to install it when using a binary package. Plus with at least a stock F27 it didn't "just work" after a make install for me.

after installing mongo c++ drivers changed code to cd into home dirctory before removing /tmp/mongodb-cxx-driver directory

added building mongodb_plugin to cmake options, fixed potential issue with libtool when installing on a clean darwin OS and the default version of libtool

Added support for installing MongoDB via homebrew and compiling mongo-c-driver-1.9.3 && mongo-cxx-driver to darwin OS

compute the disk capacity based on block sizes and counts so ha terabyte capacity drives do not break the script