Given an interval [a, b), a function f: nat -> T, a predicate P, and a
total, reflexive, transitive relation R, [search_arg f P R a b] will
find the x in [a, b) that is an extremum w.r.t. R among all elements x
in [a, b) for which (f x) satisfies P.

For example, this can be used to search in a schedule for a scheduled
job released before some reference time with the earliest deadline.

Points before or after an interval are not in the interval...

n + a - b + b - a = n if n >= b

...to match leq_ltn_trans in ssrnat

The proof got stuck at the goal of

	 {in l1, forall x0 : T, x0 != x}

which requires unfolding of prop_in1 to get at the x0 before intros
can be effective.

- Remove Require declarations from Modules.
- Small fixes due to changes in the type checker.
- Generate _CoqProject with Makefile and remove spurious warnings from ssreflect.

This commit contains several updates related to uniprocessor scheduling.

- Basic definitions of uniprocessor scheduling (see model/uni)
- Definitions of worload and service for generic sets of jobs (see service.v and workload.v in model/uni)
- Definitions and lemmas about busy intervals (see model/uni/basic/busy_interval.v)
- Definition of an arrival bound for sporadic tasks (see model/arrival_bounds.v)
- Definitions and correctness proofs of the RTA for FP scheduling
  (also works with non-unique priorities and arbitrary deadlines, but gives pessimistic bounds)
- Implementation of the FP RTA to check for contradictory assumptions

In addition, we have also defined partitioned scheduling and proven how it relates
with uniprocessor (see model/partitioned).

- 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