Make it easy for Child Algorithms to post progress through their parent

[Nick Draper]

Extend the CreateSubAlgorithm method to take another two Paramters.

• ProgessScaleFactor default 1
• ProgressOffset default 0

Then wire up the parent algorithm to listen to the progress events of the child scale and offset them appropriately and then send them from the parent.

Warning: consider that there may be more than one sub algorithm per parent.

RebinToWorkspace is a good example case for the need for this.

[Roman Tolchenov]

(In [1955]) Algorithm::createSubAlgorithm has two new arguments: double startProgress, and double endProgress. These will specify what portion of the overall progress the child algorithm will take. The child's progress will be scaled down and retransmitted automatically. re #379.

[Roman Tolchenov]

(In [1965]) re #379. Added class Progress which makes progress reporting even easier (I hope). Also AlgorithmObserver class is designed to make tests of algorithm notifications easier.

[Stuart Campbell]

This ticket has been transferred to github issue ​1227