馃搱 Stacked Line Charts and several small improvements This release adds `--stacked` support for line plots. The (still quite limited) `--barplot`s keep being available and are fixed in this release. Further improvements: - apply `--style` after `--xkcd` to override the XKCD styling - catch errors in modifier handlers - environment variables `HLEDGER_PLOT_TREND_MIN_DIGITS` and `HLEDGER_PLOT_TREND_MIN_PLACES` to control displayed digits in `--trend` parameters (see `hledger-plot --help` for more info) and don't use scientific notation by default. - prevent `--trend` from matching other trends - fix `--barplot` error - rename `--drop` option to `--remove` as it conflicts with `hledger ... --drop`