Allow source location to be overridden

By default the configure script assumes that the source is located
relative to the script itself. By allowing this to be overridden, the
script can be shared by other projects, each passing their own location
as an extra parameter.
Provide a module file to "build" with dunecontrol

Having this allows us to declare a dependency to opm-build in the
other projects.
Ignore editor backup files in version control
Search for build macros in sibling directory

Instead of assuming that the entire build system macros are located
in a subdirectory of our own, then allow us to look for it in a
sibling directory, sharing the build system amongst projects.
Project build description to install macros on system

By having a project file just like all the others, this project can
be installed through a script/loop which iterates over all the modules.