New Mirari

Mirari now defines a configuration type for each possible implementation of the module types defined in mirage-types. It then generates the right files to be able to compile the projet for the different backends.
Use oasis
Add some basic test (which are currently failing)
Update autogen files
Update test
Update the tests
Upate _oasis
Update autogen files
More improvements

* add a clean command
* generate a valid Makefile
* start the jobs after evaluating their arguments
* expose V1 which specialize signature from mirage-types/V1 using Lwt.t instead of an abstract io