Up-fast-downward

- exploit better support for anytime planners in the up: this is not
a functional change but most of the necessary functionality is now provided
by the up library, so we du not have to duplicate it in the engine
integration.

- follow changes in up:
add and rename fluents in problem kind; This enables the Fast Downward
integration to use the values of static numeric fluents for action costs.
- add MinimizeActionsCost metric to both grounders

- FastDownwardPDDLPlanner:
- support anytime operation mode
- support specification of aliases and search configurations to be used by
Fast Downward
- support specification of translator options to be used by Fast Downward
- support specification of search time limit for Fast Downward (necessary
for usage of portfolios)
- support setting the log level used by Fast Downward
- FastDownwardOptimalPDDLPlanner:
- support setting the log level used by Fast Downward
- FastDownwardGrounder:
- follow changes made in UP
- credits: mention people behind the heuristics we use in the default
configurations
- use latest Fast Downward version
- common base class for satisficing and optimal solver engines
- code quality improvements: typing information and style fixes
- added jupyter notebook with examples

- follow change in up:
rename problem.env into problem.environment

- fix broken setup.py

- add grounders