Fixed Statistics for Tasks

Features

• JSON serialization implemented
• Fully self-contained pip distribution (without the need to copy ./views any more): https://pypi.org/project/pyexpool/
• Query format limit parameter applied to both tasks and jobs
• Query filters with optional values

Fixes

• [Relative] import under Python3
• Listing of the hierarchical tasks (repetitive separate listing of subtasks omitted)
• Processing of hierarchical subtasks:
  • tasks finalization
  • numterm evaluation
• Zombie apps cleaned even without the user signal
• Subtasks counting fixed

Breaking Changes

Query format jlim parameter refactored to limit and its functionality extended