Properly encode filter string in feature editor

Currently if one uses a filter in a feature import that happens to use
special characters like '&' that require encoding as an entity saving
the feature will break the XML as it will write out the literal value
but not the encoded entity. One then has to manually fix up the results.

This now uses the PDEXMLHelper.getWritableAttributeString to properly
encode this as and attribute value before writing.

Author: laeubi

ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/feature/FeatureImport.java

@@ -33,6 +33,7 @@
 import org.eclipse.pde.internal.core.ifeature.IFeature;
 import org.eclipse.pde.internal.core.ifeature.IFeatureImport;
 import org.eclipse.pde.internal.core.ifeature.IFeatureModel;
+import org.eclipse.pde.internal.core.util.PDEXMLHelper;
 import org.eclipse.pde.internal.core.util.VersionUtil;
 import org.w3c.dom.Node;
 
@@ -188,8 +189,9 @@ public void write(String indent, PrintWriter writer) {
 		if (fPatch) {
 			writer.print(" patch=\"true\""); //$NON-NLS-1$
 		}
-		if (fFilter != null) {
-			writer.print(" filter=\"" + fFilter + "\""); //$NON-NLS-1$ //$NON-NLS-2$
+		String writableString = PDEXMLHelper.getWritableAttributeString(fFilter);
+		if (!writableString.isBlank()) {
+			writer.print(" filter=\"" + writableString + "\""); //$NON-NLS-1$ //$NON-NLS-2$
 		}
 		writer.println("/>"); //$NON-NLS-1$
 	}