Refactor execute stuff to make it support pluggable compute backends

Test Plan: -

Reviewers: marcua

Reviewed By: marcua

Differential Revision: https://phabricator.locu.com/D7714
Deployment readme

Test Plan: -

Reviewers: lydia, dyschultz, marcua

Reviewed By: marcua

Differential Revision: https://phabricator.locu.com/D7739
Changes for PyPI

Test Plan: -

Reviewers: lydia, dyschultz, marcua

Reviewed By: marcua

Differential Revision: https://phabricator.locu.com/D7752
Add pykronos to requirements.txt and remove symlinks

Test Plan: -

Reviewers: lydia, dyschultz, marcua

Reviewed By: marcua

Differential Revision: https://phabricator.locu.com/D7756
Date functions, test data load script, fancy math operators for Value

Test Plan: -

Reviewers: dyschultz, lydia, marcua

Reviewed By: marcua

Differential Revision: https://phabricator.locu.com/D7749
Remove unused imports
Partly working backend again.
Merge branch 'master' of https://github.com/Locu/chronology into query-builder

Conflicts:
	metis/metis/core/execute/utils.py
Some fixes but revert raise in compute.py later