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
Make it easier to specify a shader
Add Material IntAttribute and face culling
Add defaultCullFace
added g3dj to DefaultAssetFilter for faster loading, fixed GWT AssetManager emu for ModelLoader, hacked GwtGL20 to return max texture units (always 16, hackady hack)
Merge pull request #419 from aspic/master

Snapvalues for Slider
fixed GwtGL20, cleaned up buffer handling in dev mode, may the fsm have mercy on us
fixed diffuse color and specular lighting in DefaultShader
Add default shaders to ant build.
Restore original code
Merge branch 'master' of https://github.com/libgdx/libgdx