Preparse the template in the parser to a tnode tree so it's cached in advance

[ianjosephwilson]

Right now we just mark out the parts with TemplateRef and then merge them with the live interpolations during processing. An optimization would be to pre-load them into the cache.

This was split out of #120

[ianjosephwilson]

In addition to checking that the component's children should parse when reached later on we also parse the children to "remove" all the placeholders that we are tracking. Otherwise when we are done with the template it might seem that we missed some. This raises an error in close(). We could probably flush these out from component start index to component end index but just another book keeping thing to remember if this pre-load thing ever happened. This is related to the TComponent.children in that by parsing the children into it we actively remove those placeholders.