soft_assert helper functions (and docs!)

Hopefully these make soft_assert more useful.
Fix force_navigate to....force_navigate
Merge pull request #668 from psav/fix_force_navigate

Fix force_navigate to....force_navigate
Merge pull request #660 from seandst/soft-asserts

soft_assert helper functions (and docs!)
Central creation of logging conf; guard agains env not having a logging conf
Add cmdline filtering of providers

Allows the usage of --use-provider to specify a provider to filter tests
by using the yaml key.