[Optimisation] compute a hash of the input parameters as a form of caching

[skinkie]

Is your feature request related to a problem? Please describe. Analogue to #510 I think there is a fundamental design problem with the way Meshroom acts on changes of graph properties, which causes significant recomputations where the outcome is rather stable. As an example, if feature matching has been done successfully, those matches are not going to change by some changes in camera properties. I can also argue that the found relations are still sound.

Describe the solution you'd like Instead of recomputing, it could also be defined what input parameters would affect outcome. This is likely a more complex framework than recomputing, but since every change causes an entire graph to reset, it should be considered and would significantly increase end-user productivity.

In the case of #510 what Meshroom would need is some sort of ability to act on a set-transition, increasing or decreasing would required some additional work, or remove results from the output. But generally speaking work that already has been done should be cached and available.