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.
This is a lot of DOM manipulation, and I'd prefer you used the `on()` alias for `addEventListener()` that is included in `util/dom2` instead of directly setting `onchange`. This also definitely makes the case for moving this functionality into another panel that can manage its own state, instead of binding to the dialog constantly.