Added distribution package for u2py

+ Compiled with py2exe.
Implemented context-based execution of requested command via Reader.pool based on gevent ThreadPool.

When there is no reader present in request, ReaderlessContext provides a way to execute such request in same thread without using thread pool.

+ Monkey patch in webapi.server required for web.py correctness.
Fixed Reader.apply method to support callbacks without arguments.
Reader detection procedure now utilizes Reader.apply to put close operation into reader own operation queue.
Unified exception handling for handlers_base