Merge branch 'master' into sed-flux-dep
New trp-lim fluvial component

This new version of the transport limited fluvial component corrects a
number of problems with previous versions, which will shortly be
removed.

It appears to give answers which are close to concavity metrics for the
analytical solution, but some further testing needed.

Code requires significant cleanup, especially the documentation.
Improving flow routing

1. Added node_diagonal_links() to raster.
2. Added raster.number_of_diagonal_links.
3. get_diagonal_list() can now take bad_index, bringing it into line
with get_neighbor_list().
4. FlowRouter now stores the return flow_sinks from
flow_accum.flow_direction() as a boolean model field.
5. flow_accum.flow_directions is now finally parallelized (no looping).
Should also be equally compatible with voronoi grids as raster, though
not yet tested.
plot.imshow functions now take fields

Several key imshow functions can now take field strings as well as
arrays as inputs.
Bringing transport_limited_fluvial to useable

transport_limited_fluvial now in full working order. Added:
1. Dynamic internal stability checking and dynamic timestepping.
2. Can output channel parameters like width, depth, etc.
3. Component can now take an input (& indeed, spatially and temporally
variable) runoff_rate.
4. Improved documentation
5. Clarified io
6. Created ideal, physically plausible set of driving parameters in a
new input file.
Merge branch 'sed-flux-dep'