Merge pull request #15 from toxeus/fixScope

cppcheck: fix variableScope in opentxs-core
Convert api lib to stream logging
Cleaned up some comments
doc: include command for cleaning submodules and repo
Merge pull request #18 from da2ce7/doc_update_clean_git

doc: include command for cleaning submodules and repo
Merge pull request #5 from BugFreeSoftware/api_stream

Convert api lib to stream logging
CMake: use system's ZMQ includes
Merge pull request #19 from toxeus/zmqIncludes

CMake: use system's ZMQ includes
cmake, SWIG: Minimum 3.0.0
INSTALL-Docs: Requires SWIG >=3.0.0
Merge pull request #20 from lclc/swigMinimum

Swig minimum 3.0.0 cmake check & docs update
cppcheck: fix variableScope