Test for connectedness when solving

[GearsAD]

GearsAD/GraffSDK.jl#103

[dehann]

Moving to next patch release to allow for new JuliaRegistrator tagging approach and other bug fixes. This function is simultaneously being introduced as part of the DFG upgrade -- tentatively scheduled for IIF v0.7.x cycle (currently in progress).

[dehann]

DFG introduces the ability to test for connectedness, must now be integrated with solver.

[dehann]

affects #129