DB48X: HP48-like RPL implementation for DM42

[c3d]

https://github.com/c3d/DB48X-on-DM42/rel...tag/v0.5.0

This release provides statistics functions, scatter and bar plots, and flags.

New features:

* Statistics (#495) and linear regression (#569)
* File-based statistics (#571)
* `Sort`, `QuickSort`, `ReverseSort`, `ReverseQuickSort` and `RevList` (#572)
* Flags, i.e. `CF`, `SF`, `FS?`, etc (#43)
* Plot scaling commands such as `SCALE`, `CENTR`, `XRNG`, ... (#582)
* Add `CurveFilling` and `DrawPlotAxes` setting flags (#580)
* `ScatterPlot` (#577) and `BarPlot` (#579)

Bugs:

* Save settings enumerations as portable text (#565)
* Avoid infinite loop when reading at end of help file
* Repair behaviour of `-1 DIG`, broken by settings improvements
* Fix definition of `rpm` in units and units file
* Crash in `list::map` when called function errors out (#570)
* Fix editor horizontal movement when inserting commands (#576)
* Repair plotting demo (#583)
* Fix vertical position of axes in `DrawAxes` (#584)
* Very long drawing loop if `ppar` axes are backwards (#585)

Improvements:

* Sets editor selection correctly for command-line errors
* Ability to parse command and setting names in quotes, e.g. `'Radians'`
* Insert command names inside quotes (#575)
* Update documentation of implemented features (#569)
* Make `PlotParameters` a keyword (#578)