Fixing typo and how ROSA_ENABLE_ASSERTIONS is handled in CMake project; refactoring handling the option ROSA_LOG_LEVEL in CMake project; adding document generation to CMake project; creating docs directory with minimal set of files for document generation (based on files from the LLVM Project); moving README.build.txt under docs as Build.rst (outside of svn due to 'bad gateway 502' after the repo was moved), reformatting the text and extending it; adding docs/Dev.rst and moving some text into it from README.txt; cleaning README.txt; adding a new file TODO with an initial list of pending things (related to documentation now).