Use clock generator 2 for TC.

Generator 3 is used by EIC, so
using EIC and TC together didn't work.
Fix digit separator, doesn't work with C code.
Improve SPI transfer..
Beginnings of DMA code.
Better define checks.
Add I2C_SYSOPBUSY for samd20 also.
Add a project file for SAMD11D14.
Fix paths, enable CTL property.
Add waits after i2c reg writes.
Solution and project files for SAMD21G18A.
d21/d2x to samd mass rename in the code.
Continue d2x to samd renamings.
More renamings.

Use platform prefix after all.
This way we don't conflict with Atmel's own files.
And even more d2x to samd renamings.
Move d2x to samd renamings.
Rename platform_atmel_d21_*.[ch] to samd_*.[ch].