* use more concise name
* add cases with [is_true _] in addition to cases with [_ = true]

This partially addresses #54.

- 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

Obviously incomplete, but a start.