Move everything into the new namespace starting with 'prosa' rather
than the bland 'rt'.

- Added definitions and implementation of jitter-aware RTA for
  uniprocessor scheduling.
- The Prosa directory was restructured to better accomodate the different
  types of arrival sequences and schedules.

- Add definitions related to APA scheduling
- Prove correctness of reduction-based RTA for APA scheduling (FP and EDF)
- Add implementation of a weak APA scheduler
- Update definition of taskset to assume uniqueness
- Modify names and comments to improve readability
- Remove strong assumptions about priority order in FP scheduling
- Add tests with FP RTA for every model
- Add tests for RTA with parallel jobs

- Removed unnecessary assumption in RTA about task precedence/no intra-task parallelism.
- Scheduler models and analyses are organized in separate modules/folders.
- Added RTA for FP and EDF for schedulers with release jitter.
- The scheduling invariants were split into more fine-grained assumptions:
  (a) scheduler is work-conserving
  (b) scheduler enforces FP/JLDP priority X
- New helper lemmas about counting, and sorted/uniq lists
- Inclusion of tactics feed and feed_n (see documentation).
- Added a Makefile generator