Implement Iterator

Design idea: "Iterates on data"

Iterator has next method to loop over a DataCollection. It returns a list of X and Y to use for an arbitry task. There could be multiple versions, e.g. a normal loop (for pre-/postprocessing) and a distributed loop (according to a batch size). The Iterator should meet all requiremnts to use in parallel for keras.

Jobs:

• has methods next to return X and Y return class object (that has get_X and get_Y)
• has an abstract class not required
• has inheritances that handle different kind of loops
  • normal loop (StandardIterator, connected with DataCollection from #142 (closed))
  • distributed loop (KerasIterator, requires DataCollection from #142 (closed) as input)

changed milestone to %Advanced data handling

added To Do enhancement refactoring labels

created merge request !117 (merged) to address this issue

mentioned in merge request !117 (merged)

marked the checklist item has methods next to return X and Y as completed

marked the checklist item has inheritances that handle different kind of loops as completed

mentioned in issue #142 (closed)

mentioned in commit 2ec987d1

added .done label and removed To Do label

mentioned in issue #144 (closed)

mentioned in issue #33 (closed)

added merged in Develop label and removed .done label

closed via merge request !135 (merged)

mentioned in commit d099bd6d