Soem fixes

-Language combobox has a fixed size
-Run button is re-enabled after switching to AppleScript and back
-Absolute path of current file is shown in title bar of the editor
-Cleanup class names and class inheritance a bit
-Fix some BadLocationExceptions (coming from asynchronous gutter update)
-Fix '+' button for new tabs (the user could have selected the small region between the button and the edge of the tab component)