Updated the synthetic migration example

Updated the synthetic migration example to use a FULL unstructured
grid. The result is the same as using the basic grid in waveloc-0.2.
Fixed grid plotting in u-grid code for FULL grids

Simplified most of the plotting calls and files down to one file and
two functions (one to automatically plot all locations, and one to plot
a single location - the first calls the second, of course). The same
code is used to plot real locations and those from synthetic tests.

Closes issue #94