Standardize Graph CRUD retry behavior

[dehann]

Suggestion 1

a CRUD operation can retry N number of times, default is 2 or 3, but set via keyword arguments so the behavior can be disabled by the user.

fg = inifg(Cloud)

addVariable!(fg, :x1, Pose2, retries=1)

[Affie]

I don't know if retry belongs in DFG? My first thought is that it should rather be in the next level, eg RoME.

[GearsAD]

Rather let this be done by the user or wrapper is my feeling. If we embed too much logic in the API, then it gets more complex.