config loader, yesno(): use str_to_bool()
console/interpreter: minor improvements

* added --clear option to "history" command
* "set" can now be called without VAR=VALUE
minor cleanup
set default EAPI=5 and make it configurable

SLOTted dependency rules allow to use EAPI 5 features, so default to 5.
roverlay/depres, slot rules: fix get_slot_result()
roverlay/depres/depenv: skip vmod dict lookup

When checking/normalizing vmod_str, set vmod directly if possible.
tests/depres.py: print test data identifier

Helps when tests fail.
tests, data: reflect SLOT rule changes
doc/rst: fix slot rule examples
update generated files
roverlay 0.3.1