Processing enhancements

This commit:

* Ensures a minimum of 5 threads within the Thread Pool at
initialization (1~4 are consumed by the system, leaving at least 1
available for other invocations).
* Changes Process::PRE_INIT to Process::INVOKED, denoting that the
(0x01) flag represents that a Process is started (but may not yet be
initialized).
* Allows all Process implementers to define their own sleep time when
suspended.  This can only be changed internally via either the
@sleep_time instance variable or the #sleep_time=() protected method.
Default duration is 0.01 seconds.
* The .invoke_processes() method of Arpk now discovers all Process
implementers and will .execute() them if and only if they are not
already invoked.
* Tiny bootstrap update for better handling of the --resolution switch.