First pass at proper POMs for building and packaging things.

The gdx-tools artifact even properly bundles the various extra jars into
itself. The only thing still missing is a POM to create the gdx-platform
artifacts, which I'll tackle next.
Name the parent gdx-parent.

Everything else is gdx-something, so it's weird that parent is bare.
Maven wiring to build natives jars.

This currently downloads the jars from the build server. It may be possible to
have Maven actually do the native builds, but that seems like perhaps more
trouble than it's worth.
Allow running particle editor via Maven.

From the top-level directory:

mvn -f extensions/gdx-tools/pom.xml test -Pparticles
Merge branch 'poms' of https://github.com/samskivert/libgdx into maven
Merge branch 'poms' of https://github.com/samskivert/libgdx into maven
manually merged changes to platform/pom.xml by Michael
Merge branch 'master' into maven
Merge branch 'maven' of https://github.com/libgdx/libgdx into maven
Merge branch 'master' into maven
Remove non working test models
Merge branch 'master' of https://github.com/libgdx/libgdx
Rename NewModelTest to ModelTest, add Basic3DTest
Remove debug logging
Add head and teapot model, add async loading to the tests
Merge pull request #417 from xoppa/master

Remove non working test models, add Basic3DTest, rename ModelTest
Make it easier to specify a shader
Add Material IntAttribute and face culling
Add defaultCullFace
Add classpath files support for gwt (limited)

Classpath files, such as the default bitmap font and the default shaders
for the new 3d api, are now available in gwt. This limited support
requires the classpath files to be specified in the gwt module definition
by setting the multi-valued property 'gdx.files.classpath'. Any file
specified will be copied to the assets folder at compile time.