Add AIXMLLindenGenepool - redo of archetype export/import using AIXML*.

In order to remove code duplication, and as prove of concept,
I redid the linden_genepool archetype export and import (from the Edit
Appearance Floater), using AIXML and AIAlert.

The import/export code did shrink significantly, and became a lot
simpler. Although a new file pair (aixmllindengenepool.{cpp,h}) is
added to define the (de)serialization of the linden_genepool XML format,
that code is now centralized in one place, and still a lot simpler.

As a bonus however, every possible error is now semi-automatically
reported to the user with all details that might help to overcome
the problem, like file names and system errors.

indra/llappearance/llpolymorph.h

@@ -173,6 +173,7 @@ public:
 	// LLVisualParam Virtual functions
 	///*virtual*/ BOOL				parseData(LLXmlTreeNode* node);
 	/*virtual*/ void				apply( ESex sex );
+	/*virtual*/ char const*			getTypeString(void) const { return "param_morph"; }
 	
 	// LLViewerVisualParam Virtual functions
 	/*virtual*/ F32					getTotalDistortion();