Cache incidence matrix

[vyudu]

For functions that use the incidence matrix (isreversible, isweaklyreversible, deficiency, linkageclasses, etc.) have them construct the incidence matrix internally instead of having the user call reactioncomplexes first.

[isaacsas]

Make sure to update the docstrings of any functions that now handle caching (which may mention users previously needed to call reactioncomplexes first...). For example, incidencematgraph.