Averaging phase continuation

[PKua007]

One should be able to continue the averaging phase - for now, it is redone form scratch if interrupted.

[PKua007]

Averaging phase may be continued using RAMTRJ recording. This however requires averaging step size to be the same as snapshot step size. This may not be optimal, especially for correctly estimated errors. This change should be done together with correlation time computation, which is not planned for the First binary release milestone.