Add support to check for program updates (no automatic update yet)
* New option in Tools -> Options -> Advanced to disable update check during program start
When compiled in DEBUG mode, automatic check is disabled but check can still be attempted from Menu Help -> Check for program updates
* New class for doing async web requests for the update checker

Update Issue 201
Support has been added for checking for updates to the program, automatically updating the program is not yet supported

git-svn-id: http://superputty.googlecode.com/svn/trunk@401 8d6e282c-8220-11de-b77e-d9b456c0130a