Need to devise a thread-safe method for setting values at run-time

[sbabcoc]

Currently, the only way to set configured values at run-time is through system properties. This method is inherently unsafe in multi-threaded execution, as system properties are visible to every thread within a single process. We need a method to set values in a thread-safe manner, and we should document the process-global nature of values set via system properties (which is desirable in some scenarios).