Added functionality to change between a SMA trend and an EMA one.
When the (progressive) option is selected in the trend, the MA is progressively generated from the very first value.
Classic N-length MAs (not progressive) ignore the first N-1 bars and continue from the Nth one.
Do note that for now, you may only choose as input the main data source. There is some functionality that needs to be fixed for you to use this indicator on top of other indicators.