get_feature_vector() method into two separate functions so the interface
is a little simpler and more flexible.

backwards compatibility with the previous version though.

strengths from the object_detector.

difficult, truncated, and occluded metadata fields of the pascal datasets.

to 100 rectangles.  This has been removed.

matrices.

as the feature vector type.

it does a saturating add rather than a normal add.  This ensures the
probability value stays exactly <= 1.  Previously, floating point
rounding error could cause it to be slightly above 1 and would therefore
cause some asserts to misfire during debugging mode.

the feature extractor.  Also added the necessary input validation
to make sure this feature doesn't get misused.

added some tests to make sure the code really does work with the
relaxed interface.

a copy by value.