Remove obsolete Ant configuration

We should not support unnecessarily different ways to build. Maven it is.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Document how to build the beast

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Merge pull request #2 from openspim/how-to-build

Document how to build the plugin