Initial Bazel build definition

[odisseus]

How to:

• Build all sources

bazel build //...

• Run all tests

bazel test //...

• Run the demo

bazel run //src/main/java/io/ipfs/api/demo:demo

TODO:

• Create a target for building the distribution JAR
• Clean up the remains of the Ant and Maven build definitions

Questions:

• [ ] How to set up artifact publishing?
• [x] Is it possible to import java-multiaddr etc. as source repositories instead of importing the published JARs?