DB48X: HP48-like RPL implementation for DM42

[c3d]

Release v0.7.16 has just been published.

The focus of this release is on new commands, notably for matrix and vector operations. This release also ships with a DM48X-specific keymap, which fixes a problem with teh file selector on the DM32. The equation library has been extended with numerous equations, but they are not fully validated yet.

- con, idn and ranm matrix generation commands
- Array→ and →Array commands to convert array to/from stack
- dot product and cross product commands for vectors
- DispXY styled text rendering command
- DupDup command duplicating top item twice
- Add a large number of equations to equation library