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/llcharacter/llvisualparam.h

@@ -162,6 +162,10 @@ public:
 	void					setParamLocation(EParamLocation loc);
 	EParamLocation			getParamLocation() const { return mParamLocation; }
 
+	// Singu extensions. Used for dumping the archtype.
+	virtual char const*		getTypeString(void) const = 0;
+	virtual std::string		getDumpWearableTypeName(void) const = 0;
+
 protected:
 	F32					mCurWeight;			// current weight
 	F32					mLastWeight;		// last weight