Issue finding cells in interpolate

Hi @fverdugo,

there is an error in the algorithm for finding the cell where a given point lies for unstructured grids. This error is manifested when a point lies in an element whose vertices are not the closes vertex to the point. See for instance the following example:

:

One possibility for a workaround would be to find through the neighboring elements if no cell is found in the first pass. But I'm not sure if this is efficient and I don't know how to implement it in the most efficient manner. Any ideas?