Make H2O able to be embedded

Rename src/init --> src/H2OInit
Rename build/hexbase_impl.jar --> build/h2o_core.jar
Add test-src/embedded/SampleMain.java
Compiles with "javac -cp h2o.jar SampleMain.java".  Runs the same.
Add horrible interface delegation mechanism to cover over the
classload reweaving issues.  All external calls go through
src/H2OInit/External.java which makes a golden object of interface
ExternalInterface, and of type water/InternalInterface.  Then this
golden object delegates the call(s) but gets the right classloading
context in place.
Merge branch 'master' of github.com:0xdata/h2o

Conflicts:
	build.sh