Add ability to search all files in the project

Adds a "Find in Project" option to the "Project" menu and a "search" function to the ProjectManager.  Regular expression and multiline queries are supported.  Clicking a result will open the file (if not open already) and move the editor's cursor to the appropriate line and column.  I have plans to make this a combination "Find / Replace in Project".  Let me know if you have any questions.
Using file locks seems like much more trouble than using the async utility functions that are available in `util/manos`. Check those out--they are largely similar to caolan's async library, and with a little tweaking would make this process a lot easier for you. If there's something you need added to that library, let's do that instead of trying to reimplement a common pattern here in one place.