build: create an OMakeroot file (build lib & app)

This relates to #108, the current OMakeroot builds the library,
installs it, and build the `biocaml` application.
Delete gff_counts old-app
Delete gff_to_bed old-app
Delete gff_to_table old-app
Delete sgr_to_wig old-app
Delete wig_correlate old-app
Delete `lwt_tests` obsolete benchmarks
build: add unit-tests to OMakeroot (#108)
build: add `benchmark_zip` to `OMakeroot` (#108)
build: remove `_oasis` file
build: add the `(un)install_app` targets (#108)
build: clean-up OMakeroot (#108)
build: add the `doc` target (#108)
build: add target `install_doc` (#108)
build: add the `dist` target (#108)

The tarball is now created in _build/dist/ with its MD5 sum file.
build: add the TAGS target (#108)
build: make build of app/tests configurable (#108)
build: remove obsolete Makefile
build: add a `configure` target to the OMakefile
doc: update INSTALL file