Added options for cmake_build_type, codeCoverage & doxygen. Added check for directory script is being run from

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

Don't set the cmake variable OPENSSL_LIBRARIES. It's very clear from the documentation that that's an output variable. Not an input variable.

This resolves a benign but worrisome warning from cmake on chainbase_test.

Build all dist's. Added dynamic CMAKE_BUILD_TYPE. Default is CMAKE_BUILD_TYPE=Release. Set env var EOS_BUILD_TYPE=[Debug|Release|RelWithDebInfo|MinSizeRel] to enable.

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

Issue #1929

Ubuntu: moved mongodb install to /home/bhamilton/opt/mongodb formatting changes for ease of readability

added additional system and build information to eosio_build.sh. Added EOSIO information and links to end of build