Implementation of OffsetFilter

This PR includes a new Filter, `OffsetFilter` to filter items from the beginning and/or the end of the Workflow.

As far as a `Filter` cannot tell `Workflow` that the processing of the whole process can be stopped, there is still some overhead when the max count is met and the read file/source contains more lines.

`new OffsetFilter(0, null);` is the default implementation, where the whole file is read.
`new OffsetFilter(0, 5);` reads max. 5 lines from the beginning
`new OffsetFilter(5);` starts reading from line 5 to the end of the file
`new OffsetFilter(2, 2);` reads lines 3-4