Add linker scripts to project folders

[lstandage]

The linker scripts should be in the corresponding project folder, in order to allow the customer to see what is being used.

(This also avoids the path dependency mentioned in another issue.)

[gholdys]

As far as I remember, I tried adding the .ld scripts to this folder but it didn't work well - the MPLAB X IDE passed only the first file from this folder to the compiler and we need two files. I'll double check that...