Add the ability to specify directions with words or chars

[Tim55667757]

Add the ability to specify directions with words up, down, no or chars u, d, n for the --split-trend key, in addition to the existing ability to set up the trend with symbols /\-.

To separate words or chars use the hyphen symbol, e.g. --split-trend=up-down-no-up, --split-trend=u-d-n-u etc.