Use proper naming for bases, node-factories, and node-factory builders

When introducing the concept for the reusable part of a basis we used the name *NodeFactory. It was clear from the beginning, that this is misleading, because it does equally well create index sets. Later we also introduced the size(prefix) such that the name *NodeFactory really does not fit its purpose. On the other hand we now have real factory objects (the guys that you get by calling 'lagrange(...), composite(...), ...) whose only purpose is to create a NodeFactory. Because I was scared of *NodeFactoryFactory or Meta*NodeFactorythese are called *NodeFactoryBuilder which I'm really unhappy with. The issue became even more clear, when I tried to describe what these guys are doing in the docs. So here's my proposal:

Since the current *NodeFactory is the reusable core of a basis, I propose to call it *BasisCore. Then the current *NodeFactoryBuilder could be called *BasisCoreFactory which exactly describes what it does. I'm open for better alternatives to *Core* but *NodeFactory really is not what it does. Since it seems that at least 4 people (me included) would like to have some kind of 2.5-release, I'd like to fix this rather now than later. Opinions?

Notice that, until someone explicitly used our NodeFactories instead of the bases, renaming these guys will not effect user code.