The latter was prompted by the fact that assert_equal did not like mixing LinearFactor and MutableLinearFactor
But MutableLinearFactor always was a bit of a kluge. We should eradicate all non-const on LinearFactor some other way.
smallExample was changed to include two of the examples used in testConstrainedLinearFactorGraph
ConditionalGaussian was changed to make solve() virtual, as this is necessary for ConstrainedConditionalGaussian
''Limitations: ''
* Any given node can only have one constraint on it, but constraints can be of arbitrary size
* Constraints can only be specified as a blockwise system, where each block must be square and invertible to support arbitrary elimination orderings.
* ConstrainedNonlinearFactorGraph is disabled until a better solution for handling constraints in the nonlinear case is determined.
Frank Dellaert
Alex Cunningham
Richard Roberts