Add the std.idioms module - a common idioms library.

Currently 3 idioms are implemented:

* Properties -           Generate property getter and setter accessors
                         for member fields.
* LowLockSingleton -     Turns the class into a singleon, using David
						 Simcha's and Alexander Terekhov's low lock
						 singleton implementation approach.
* ThreadLocalSingleton - Turns the class into a thread local singleton.