added out-of-source build directory

- includes .gitignore to ignore any files in this directory
- will be used as default CMake build directory
restructured source files

- moved includes to ./include
- renamed main.cc to main.cxx (will compile to an executable)
extended .gitignore w/ typical files not intended for VC
added first CMake configuration file

- set to compile shared library and executable
- uses git to determine version number from last tag (otherwise uses hard-coded value)
- sets RPATH for libraries
- includes several CMake files for compatability w/ earlier versions, C++11 support and printout of config summary
- includes ROOT search script and (commented) CMake config for later use
added doxygen configuration

- already included in CMake config -- run 'make doxygen' to generate