Maven-ize java_dann_examples & create parent project files

* sources and resources were only moved, not changed
* moved test sources into separate dir
* adjusted ant build script (targets tested)
* added Maven project file (projects/java_dann_examples/pom.xml)
* added Maven parent project file (projects/dann/pom.xml)
* moved some stuff into parent project, to reduce duplication
* added all-projects maven file for convenience (projects/pom.xml)
* added maven build dirs to gitignore
* renamed dann to dann-core (maven artifactId)

To build all of dann (core + examples), use either of:
* projects/dann/pom.xml
* projects/pom.xml

To build only core, use:
* projects/java_dann/pom.xml

It is NOT possible to build the examples directly with:
* projects/java_dann_examples/pom.xml
Except you have the required version of dann-core deployed
into your (local) maven repo with:

	cd projects/java_dann/
	mvn install