parse None/True/False in engine_from_config (for pool_reset_on_return)

[Daniel Kraus]

engine_from_config doesn't translate .ini true/false/None values to their python counterparts which means "pool_reset_on_return = None" doesn't work. (only 'commit' or 'rollback')

[Mike Bayer]

• Added the string value "none" to those accepted by the :paramref:.Pool.reset_on_return parameter as a synonym for None, so that string values can be used for all settings, allowing .ini file utilities like :func:.engine_from_config to be usable without issue. fixes #3375

→ <<cset c2e300250324>>

[Mike Bayer]

• Added the string value "none" to those accepted by the :paramref:.Pool.reset_on_return parameter as a synonym for None, so that string values can be used for all settings, allowing .ini file utilities like :func:.engine_from_config to be usable without issue. fixes #3375

(cherry picked from commit c2e3002503242331fc8f2b314e0d4f3c65de9d73)

→ <<cset 384c885ed078>>

[Mike Bayer]

thanks for reporting!