Merge pull request #12 from vbmithr/master

Clean generated "filesystems" while cleaning
Import an updated version of avsm's ec2.sh AMI bundling script

Signed-off-by: Mike McClurg <mike.mcclurg@citrix.com>
Merge pull request #13 from mcclurmc/ec2-script

Import an updated version of avsm's ec2.sh AMI bundling script
mirari run --unix now runs unikernels for the UNIX backend.
Add fd-send-recv as a dependency for unikernels if target is unix-direct
Better error message on Ctrl+C
Put an IP on tapX, in order for tuntaposx to work.
bump to 0.9.3
Do not use OPAM compiler switches any more, as that's done in the packaging now
correct example ip
compile with annot files by default
Use explicit command-line flags to pass through the --unix and --xen compiler switches.

This requires the latest OPAM package specifications, and is part 1 of a commit series
force the installation of mirage-unix or mirage-xen depending on the backend
split out util functions
Add a `--socket` flag to activate socket-based networking (UNIX only).
do not make install depend on build to make sudo installations easier
mark 0.9.3
mirari run for --socket and --xen working (via xl).