Style Enhancements, and add styles from Chandrakant

[DanielGoldfarb]

Enhancements to styles:

• allow volume_alpha from within styles.
• implement separate color for volume bar edges (the token vcedge was already in several styles, but had not been implemented in the code).
• allow scale width adjustment from withing style: set up dict the same as if for mpf.plot() kwarg scale_width_adjustment

Add styles "binancedark" and "tradingview" created by Chandrakant (and modified slightly by me taking into account the above three enhancements)