Source files moved to "/src" folder

All source files including tests were moved to "/src" folder. This is
the first step for "nupic.core" be build from "nupic".
External API and headers moved to "/external" folder.

Only external API and headers used by "nupic.core" were moved. Binaries
like "swig" remains in "nupic".
CMake updated to compile "nupic.core" in a independent way
A improved version of CMake file

-Removed Python stuff;
-Removed unused code;
Compliance with the new structure of directories
Fixed -lc++abi issue
Fixed -gfull issue
Added build instructions to README.

Updated gitignore to ignore test hpps.
Merge pull request #1 from rhyolight/core-build

Added build instructions to README.
Changed "cmake $REPOSITORY" to "cmake $REPOSITORY/src"
Included "Using graphical interface" instructions
Changed "Open 'Nupic.*proj'" to "Open 'nupic.core.*proj'"
Updating SHA
"ie" replaced by "i.e."
Removed "unit tests" folders (unit tests already are in "testeverything" folder)
Replaced "nupic.core" to "nupic_core" (compliance with file name convention)
Merge pull request #47 from DavidRagazzi/master

Independent Build Process