''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.
* Factors are now templated on the configuration type. Factor Graphs are now templated on the factor type and configuration type.
* LinearFactor is a factor on an FGConfig.
* LinearFactorGraph uses LinearFactor and FGConfig.
* NonLinearFactor is still templated on Config.
* NonLinearFactorGraph uses NonLinearFactors, but is still templated on Config.
* Tests and VSLAMFactor have been updated to reflect those changes.
Frank Dellaert
Alex Cunningham
Richard Roberts