fix -for-pack build error

The sed command was producing `uriakc` as the pack name. Replaced with
hard-coded `Riakc`.
convert build system to use OMake

Compilation of examples and tests is still buggy.
update .gitignore
OMakeroot: auto-generate list of examples
OMakeroot: tests now compiles correctly

Needed to vmount the tests directory.
examples/.gitignore: remove since it is now superfluous

Compiled files now all go under _build.
OMakeroot: remove async_core dependency

Core has been restructured. This is no longer a package.
all_tests.ml: fix type error

I’m guessing Robj interface was changed at some point.
OMakeroot: clean up a bit

No major changes.
provide local opam package

This local copy can be copied to the main opam-repository for official
releases. In the mean time, developers can add this as a repo to use
latest build instructions.
re-arrange directories

Put examples/ and tests/ under new src/.
Rename lib/riakc/ to src/lib/.