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.
I'm not sure that a tab is the right vehicle for the results.  One of the nice features currently implemented is that you can click a result and have it take you to the line / column in question.  I'll look into using the palette.