We almost always only want the weak safety (checking that output signals
of the main component are deterministic), not strong safety
(checking that all signals are deterministic). However, currently the
strong safety mode is the default. This makes it cumbersome to invoke
Picus, since we need to indicate that we want the weak safety explicitly.
This commit inverts the behavior by removing the flag `--weak` and
adds the flag `--strong` (for strong safety), which is defaulted to false.
8432a9bfb6