Add time offset and fix ceres 2.2 compile

[caillotantoine]

Add time offset:

In the step 1, I added the --t_offset option as implemented in the original evo. Same behavior, I just passed the argument.

ceres 2.2 compile:

When I installed ceres, the step 2 wouldn't compile. It seems the name has changed for the parameters. Doc of Ceres on Problem::AddParameterBlock this seem to fit