[SCL] MACD DoubleCross

Counts crosses of the MACD and signal lines and derives entry signals. The code for counting the crosses, for deciding what counts as "close enough", and for auto-adjusting for resolutions 1D or longer, might be useful for Pinescripters. The entries and exits themselves are not intended to be used on their own, but could be used as confluence within a trading system. Full explanation is in the script introduction.