Remove the use of Ant builders

[pcdavid]

The various example projects have Ant-based builders setup in their .project:

bundles/org.eclipse.gmf.examples.runtime.diagram.geoshapes/.project
22:			<name>org.eclipse.ui.externaltools.ExternalToolBuilder</name>

bundles/org.eclipse.gmf.examples.runtime.diagram.logic/.project
22:			<name>org.eclipse.ui.externaltools.ExternalToolBuilder</name>

bundles/org.eclipse.gmf.examples.runtime.diagram.logic.model.edit/.project
24:			<name>org.eclipse.ui.externaltools.ExternalToolBuilder</name>

bundles/org.eclipse.gmf.examples.runtime.diagram.logic.model/.project
24:			<name>org.eclipse.ui.externaltools.ExternalToolBuilder</name>

bundles/org.eclipse.gmf.examples.runtime.common.service/.project
24:			<name>org.eclipse.ui.externaltools.ExternalToolBuilder</name>

bundles/org.eclipse.gmf.examples.runtime.emf.clipboard/.project
24:			<name>org.eclipse.ui.externaltools.ExternalToolBuilder</name>

bundles/org.eclipse.gmf.examples.runtime.diagram.layout/.project
22:			<name>org.eclipse.ui.externaltools.ExternalToolBuilder</name>

bundles/org.eclipse.gmf.examples.runtime.diagram.logic.model.editor/.project
24:			<name>org.eclipse.ui.externaltools.ExternalToolBuilder</name>

bundles/org.eclipse.gmf.examples.runtime.diagram.decorator/.project
22:			<name>org.eclipse.ui.externaltools.ExternalToolBuilder</name>

This triggers Ant-based builds in the IDE just to produce zip files which are only useful in an actual build.

Also, Ant is old tech that I have not used personally for a long time, and has all kinds of issues in a modern environment, e.g.:

• https://bugs.eclipse.org/bugs/show_bug.cgi?id=575210
• https://www.eclipse.org/lists/cross-project-issues-dev/msg19778.html