bye bye harmonics weight 5

[giacomomagni]

To facilitate #202 and delete unused stuff, we move the harmonics weight 5 in an independent package provided in extras.
Note that only S5 and Sm5 will remain in eko (since they are actually used).

[t7phy]

To facilitate #202 and delete unused stuff, we move the harmonics weight 5 in an independent package provided in extras. Note that only S5 and Sm5 will remain in eko (since they are actually used).

But what is the purpose of separating it? This would break the cache in #202

[giacomomagni]

But what is the purpose of separating it? This would break the cache in #202

These functions are never used inside any expression implemented in ekore so far (I hope you won't need them as well. Note that S5 and Sm5 will remain in ekore),
so they are actually a leftover of an old implementation of some N3LO matching condition which is now given parametrised. Keeping them in ekore is just slowing down the compilation and maintenance.

[alecandido]

Definitely fine. I added a couple of suggested simplifications to the package, but you can even skip and merge. As you wish.