collada. Fix to read source data.

Fix when reading source array. Previously only a single array value was stored in the source container.
Added a test to check source array is a multiple of source dimension.
collada. Add reading geometry mesh vertices.

Add a vertices container.
Read collada vertices, and vertices input nodes.
collada. Add an input node container.

Change vertices to use an input node container instead of holding the input directly.
The input node container will also be used in a polylist in the future.