Refactor Align

[iliatimofeev]

Currently Aling has tree responsibility:

• manage moving window
• align markdown and transcript
• add timestamps to resulting markdown

It should be splitted into:

• ActiveBlock that provides iterator and hide position in transcript.
• FormattedResult that converts part of formatted block into result
• Most of next_block implementation should be in Transcript
• Current Align should concentrate on the sliding window of the active block.