Folders reorganisation

[theogf]

I think our folder structure is a bit confusing. Right now we have:

• kernels
• basekernels
• mokernels

Whereas our data structure is :

• Kernel
  • SimpleKernel
  • MOKernel

Should we have:

• One folder compositekernels for kernels based on another kernel(s), TransformedKernel, ScaledKernel etc...
• One folder for kernels all the standard kernels (we could consider having a subfolder for simplekernels
• And keep the existing folder for mokernels