Updated Velocity Version

The new version (1.7) provides some nifty features like foreach.
generate.groovy: Add support for map and list values in .list files.

This opens a wide variety of new possibilities in template files. Syntax
for maps and lists is similar to velocity syntax.
Example: {key:value,list:[a,b,c]}

This commit also changes splitting of value pairs from .list files.
Add test for new functionality in generate.groovy
Add .vm and .list for arithmetic interfaces
Add .vm and .list for RealType implementations of arithmetic interfaces

The variables meanings can be described as:

imports - list of additional imports, see .vm for already imported packages.
javadoc - main javadoc for generated class.
interface - arithmetic interface which is implemented by this op.
authors - list of authors which will be added as javadoc @author
compute_expr - (optional) if this is set, it will be used as the expression to
	set the output to: ```output.setReal(${compute_expr});```
compute_body - (optional) if this is set, the contents of this variable will
	be inserted into the compute method.
omit_return - (optional) set to anything to not add ```return output;``` at
	the end of the compute method. This may be used if this statement al-
	ready exists in the compute_body.
constructor - Additional code to add to the contructor of this op.
members - List of members, which are represented as a map of properties:
		name - member name
		type - member type (default: double)
		modifiers - string of modifiers, e.g. "static final". Private
			is allways prepended.
		init - statement to set this member to in the class body
		construct - statement to set this member to in the class
			constructor
	All properties except name are optional.
WORKAROUND: Increase priority of InvertII

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
OpMatchingService: include generic params in help
Add global threshold test class

This class is for testing global threshold methods.  The initial commit has a test for Otsu threshold.  In the future tests can be added for other global threshold methods.  The Otsu test is structured as follows:

1.  Create a simple ramp test image.
2.  Threshold using ops and count the number of foreground pixels.
3.  Convert to IJ1 ImagePlus and threshold using the ImageProcessor functions
4.  Verify the count produced by the op is the same as the count produced by ImageJ1.

imglib2-ij was added as a testing scope dependency as it contains the utilities to convert to IJ1 ImagePlus.
Call countData

In 'HistogramCreate.run' a histogram class is created but the histogram data does not seem to be generated.  It seems a call to 'countData' is needed to generate the histogram of the input.
Threshold op now passed to map op

Previously a threshold of type T was passed to the map op.  However the map needs a fucntion as the third input parameter.
Threshold converted from bin number to gray level

In Otsu.java getThreshold, the threshold is calculated as a bin number.  Added code to convert it to a gray level.