That's my mega-commit you've all been waiting for.
The code for the shell share more routines with userspace apps than with kernel
units, because, well, its behavior is that of a userspace app, not a device
driver.
This created a weird situation with libraries and jump tables. Some routine
belonging to the `kernel/` directory felt weird there.
And then comes `apps/basic`, which will likely share even more code with the
shell. I was seeing myself creating huge jump tables to reuse code from the
shell. It didn't feel right.
Moreover, we'll probably want basic-like apps to optionnally replace the shell.
So here I am with this huge change in the project structure. I didn't test all
recipes on hardware yet, I will do later. I might have broken some...
But now, the structure feels better and the line between what belongs to
`kernel` and what belongs to `apps` feels clearer.
Instead of expecting a `USER_CODE` symbol to be set, we expect `.org` to be
set in all userspace glue code. This gives us more flexibility with regards to
how we manage that.
Moreover, instead of making `USER_RAMSTART` mandatory, we make it default to
the end of the binary, which is adequate in a majority of cases.
Will be useful for my upcoming mega-commit... :)
