Start a new top-level "Build" script.

This currently verifies that we have the correct version of Java
available and that Maven is installed, and then kicks off a build (not
cleaning first--we need to add a -c option) and run of the tests,
skipping the functional tests.

In the long run, it should by default run all developer tests that
run quickly and are guaranteed to be passing, producing no output
(unless asked to be verbose) when successful and just the information a
developer needs to identify the errors, when not.

Change-Id: I125ccac2722fe77e21d288124f370020422f736f
Build: fix broken call to error function.
Rename build.sbt -> midonet.sbt.

SBT will use any file ending in .sbt at the top level, and naming this
something other than build lets filename completion at the command line
work better for running the build script.
Build: run sbt instead of maven; added sbt check
Build: check errors when running sbt
.gitignore: ignore .build and tmp/, remove all else.
Add Todo list.
sbt: move compiled class files under .build directory.