added couple of property functions to raster.py

1. added properties: number_of_cell_columns and number_of_cell_rows to
raster.py
2. boundary_cell_count function from sgrid is a valid function. Added
anti-deprecation request.
updates to grid/hex.py and hex_lattice_tectonicizer.py
Merge branch 'master' of https://github.com/landlab/landlab
Adding functionality to generate_uniform_precip

Added two new methods to generate_uniform_precip,
yield_storm_interstorm_duration_intensity() and elapsed_time
(property). The former enables a generator interface so you can do
calls like

>>> for (interval, rain_rate) in yield_storm…intensity():
>>>    #the code

As if we don’t need to save the storm sequence, this will be a lot
faster. The iterator is smart enough to terminate and truncate the
final step according to the run_time.

The property method then provides a way for a driver using the
generator to get at the total time elapsed.
New driver for storm driven stream power

I’m playing around with using the Jordan’s storm generator to drive a
stream power model. This “works” as-is, but is pretty unstable.
tweak driver and params for storm driven SP

minor tweaks to driver etc
stream_power no longer flattens nodes

It is now forbidden for the stream_power module to completely flatten
the gradient along its flow path. It now dramatically reduces it, but
leaves 10**-6 of the incision to preserve the flow structure.

This can be reversed once we have ponding working.
Reinstating all weaves

Weave functionality has now been reinstated everywhere (I think…) I had
it, and in one other place I missed. The code implements “one time
only” weave testing on initialisation to avoid the repeated spewing of
warnings Jordan and Sai reported.

The odd 32-bit Windows compatibility issue remains, but now it will
just trip the initialisation flags and still run fine.

Enjoy your accelerated code!
Merge branch 'acceleration'
Promoted weave test to grid.base level

The testing for weave compiling now happens as part of the base.py grid
initialisation, so it only happens once.

Components that need to check whether weave can run or not can do so by
checking grid.weave_flag. (True if weaves will run)
Merge branch 'acceleration'
Merge remote-tracking branch 'upstream/master' into fix-landlab-test

Conflicts:
	landlab/utils/structured_grid.py