Expose candle settings in the public API

[mario4tier]

Candle settings are the documented way to tune the pattern functions — what counts as a "long" real body, a "doji", a "near" gap. The bindings are already compiled in (talib/_common.pxi), they're just not exported, so the only way to reach them today is through the private module:

import talib._ta_lib

talib._ta_lib._ta_set_candle_settings(
    talib._ta_lib.CandleSettingType.BodyLong,
    talib._ta_lib.RangeType.RealBody, 10, 2.0)

_ta_lib.pyx sets __all__ to the indicator names only, so from ._ta_lib import * in __init__.py doesn't pick them up, and __init__.py names only set_unstable_period / set_compatibility explicitly.

Proposal: export them like the other global-state setters.

• talib.set_candle_settings(setting_type, range_type, avg_period, factor)
• talib.restore_candle_default_settings(setting_type)
• talib.CandleSettingType, talib.RangeType

No getter — the C API has only TA_SetCandleSettings and TA_RestoreCandleDefaultSettings.

Why bother: Multiple occurences where visibility might help. In #624 the answer was the private call, and it was exactly what the user needed. In #119 the very first suggestion in the thread was "try different CandleSettings" — advice nobody could actually follow from the public API. #150 is in the same neighbourhood.

I may follow up with a PR as part of the coming v0.8.1 release.