Merge pull request #2 from robertwb/master

directory structure explanation
fixed directory names for all but base; still some issues
devel/{ext,bin} fixed; / needs work; devel might work
Actually fix consolidate-repos.sh (I hope)
Add Combinat goals draft from Florent Hivert
Update README.rst
README.rst: add my proposed directory structure
added post-process.sh and configuration.sh
change merge commit message
Use SAGE_SRC instead of statically set to devel
Useg SAGE_PKGS instead of statically putting spkgs in packages
more configuration variables
minor corrections
add initial gitignore, reorganize configure.sh
truely rewrite build system directory
truely rewrite mac app directory
move packages to SAGE_BUILD/pkgs
remove all old files in a single loop
start adding some patches
strip bad whitespace

very slow, would be way better if it could be done with filter-index