Assume second line of 'free' output will be memory.

Centos: added network call response checking, boost version check and numerous other clean up changes

Fedora: added error checking to all curl HTTP requests and all git network requests. Added version checking for boost libraries.

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

minor correction in linux build scripts to accomodate small disk sizes that return float when running df -h