Replace allowableConversionType with conversionGroup

[Agilulfo]

This is my attempt to fix #175

Instead of using allowableCoversionType that required to define for each scale the list of compatible scales I'm proposing to use a simpler group mechanism where a scale is part of a group of compatible scales.
A scale can be converted to any other scale of the same group.

I'm not entirely sure if this assumption is correct. please let me know if this is not the case

[github-actions]

Coverage report

Caution

Coverage does not meet threshold
Statements coverage not met for global: expected <=999999 not covered statements, but got 609

St.❔	Category	Percentage	Covered / Total
🟢	Statements	87.5% (+0.02% 🔼)	609/696
🟡	Branches	67.54%	129/191
🟡	Functions	79.87%	119/149
🟢	Lines	86.69% (+0.02% 🔼)	560/646

Test suite run success

268 tests passing in 17 suites.

Report generated by 🧪jest coverage report action from 2ade068

[musoke]

Thank you for this @Agilulfo ! This looks like a significant improvement 😀

Any idea what's going on with the failed coverage test? tests passed after rerunning.

[musoke]

@Agilulfo, I'm happy to merge as is if you want to leave the finite set of options for later.

[Agilulfo]

@musoke yeah let me try to figure out the enum

[musoke]

Thank you @Agilulfo!