add more strength implementations

[CelestialCrafter]

add strengths for bollinger bands, and (the upcoming) bollinger bands + rsi (weighted average of bollinger band and rsi strength

[CelestialCrafter]

i'll do bollinger band strength, @fou3fou3 will do custom bb rsi strength

[CelestialCrafter]

are we keeping strength or switching to a new model? @fou3fou3

[fou3fou3]

keep it for now , till we improve algorithms and add algo log