* Introduce hw-specific crt0 for core that calls e.g.: init_main_thread
* re-map core's main thread UTCB to fit the right context area location
* switch core's main thread's stack to fit the right context area location
Fix#1440
Kernel::Processor was a confusing remnant from the old scheme where we had a
Processor_driver (now Genode::Cpu) and a Processor (now Kernel::Cpu).
This commit also updates the in-code documentation and the variable and
function naming accordingly.
fix#1274