Added all sub-projects

for proj in opm-core dune-cornerpoint opm-porsol opm-upscaling opm-polymer; do
  git submodule add -b release/2013.03 http://github.com/OPM/$proj
donee
List of sub-directories that contain projects to build
Parse dependencies from module list
Capture externally specified variables
Remove variables that are never used in sub-projects
Setup a target for each sub-project
Utility to list the projects on the command-line
Instructions for use