Kernel: Made SyncRequest not pure virtual, with a default implementation of error (as this is not required for all kernel objects)

- SVC: Added ExitThread support
- SVC: Added SignalEvent support
- Thread: Added WAITTYPE_EVENT for waiting threads for event signals
- Thread: Added support for blocking on other threads to finish (e.g. Thread::Join)
- Thread: Added debug function for printing current threads ready for execution
- Thread: Removed hack/broken thread ready state code from Kernel::Reschedule
- Mutex: Moved WaitCurrentThread from SVC to Mutex::WaitSynchronization
- Event: Added support for blocking threads on event signalling

Kernel: Added missing algorithm #include for use of std::find on non-Windows platforms.

kernel: changed main thread priority to default, updated Kernel::Reschedule to use PrepareReschedule

thread: updated Reschedule to sit at a synchronization barrier when no other threads are ready for execution

thread: removed unused SwitchContext/Reschedule reason field, added missing arg parameter to SVC CreateThread

thread: moved ThreadStatus/WaitType to header, added support for arg on CreateThread, added correct CPSR reset

thread: added correct lowest thread priority, added a thread priority check, and added some comments

- cleaned up Kernel code a bit (moved stuff into namespace, fixed whitespace issues)
- added handle types for all different CTROS handles

- added ResetType enum

- reorganized some kernel thread functions
- added placeholder __KernelWaitThread_Synchronization function

- added KERNEL_DEFAULT_STACK_SIZE definition (0x4000)

- added __KernelSwitchToThread for enabling a thread
- added __KernelRotateThreadReadyQueue

added a bunch of threading code, recycled from PPSSPP, with lots of hacks in for 3DS... doesn't really do much yet. Just a jumping off point