Fix for Evaluator config value parser

[riccardosavorgnan]

Fixes the value parsing for the Evaluator classes in base.py. Tested with:

source .venv/bin/activate && python -c "
cases = [
    ('false', False), ('False', False), ('FALSE', False),
    ('0', False), ('no', False), ('No', False),
    ('true', True), ('True', True), ('1', True), ('yes', True),
    (0, False), (1, True), (False, False), (True, True),
]
for raw, expected in cases:
    if isinstance(raw, str):
        result = raw.strip().lower() not in ('false', '0', 'no')
    else:
        result = bool(raw)
    status = 'OK' if result == expected else 'FAIL'
    print(f'{status}  {repr(raw)!s:12} -> {result}')
"

OK  'false'      -> False
OK  'False'      -> False
OK  'FALSE'      -> False
OK  '0'          -> False
OK  'no'         -> False
OK  'No'         -> False
OK  'true'       -> True
OK  'True'       -> True
OK  '1'          -> True
OK  'yes'        -> True
OK  0            -> False
OK  1            -> True
OK  False        -> False
OK  True         -> True