Add in Convolution Operation

Adds an operation that will convolve a given point spread fn
(kernel) with a raster. It also include a simple Gaussian
operation to create a raster with a Gaussian distribution

Also includes tests.

This is the first of a few commits that will hopefully replace
the old kernel density with a better tested implementation
Merge pull request #207 from ahinz/topic/convolution

Add in Convolution Operation
Merge pull request #208 from jwalgran/master

Add a note to "Setting up GeoTrellis" about catalog.json location
Rearranged test hierarchy to match naming scheme.

This checkin resolves a conflict with the package geotrellis.op and the
new function geotrellis.op.
Refer to io._ ops with prefix.
Add new simple syntax for creating operations.

This checkin adds a new syntax for transforming a function into an
operation, with the op function(s), and tests.

If you define a function that returns a literal value, an operation to
be executed, or a StepResult (indicating success or failure) the function
can be turned into an operation by passing it to the op function.

For example,

1) A literal value, e.g.

   val plusOne = op { (i:Int) => i + 1 }

2) An operation to be executed:

   val localPlusOne ( (r:Raster, i:Int) => local.Add(r,i + 1) )

3) Or a StepResult (which indicates success or failure)
     val plusOne = op { (i:Int) => Result(i + 1) }
Fix typo in comments.
Removed finished TODO.
Add flatMap (& withResult), map, foreach to Operations.

flatMap (and its alias withResult) is a convenient way to
chain operations.

By adding map and foreach, we can now use scala list comprehension
syntax to compose operations.
Add placeholder filter() to Operation.
Merge pull request #210 from joshmarcus/topic/op_syntax

Add new simple syntax for creating operations.
First implementation of new rasterizeration code.
New implementation of scan-line algorithm for rasterization.

This checkin includes a new algorithm for rasterization and other
operation that involve invoking a function on cells that fall under
features.  The current implementation includes cells whose center are
within a polygon, or all cells touched by a line or point.
Add test suite for new rasterization algorithm and bug fixes.
Add LoadWKT and intermediate PolygonalZonalHistogram classes.
Add script for generating GDAL rasterization cell count.

This checkin adds a script that returns the cell count from a gdal rasterization
of a geojson file, plus adds an additional polygon test.
Add additional tests to polygon rasterization suite.
Remove numeric dependencies.
Merge pull request #216 from joshmarcus/topic/new_rasterization2

Add new rasterization and zonal summary strategy for features
Added Gdal utility class. Added import-tile command to geotrellis.