Editor Tab Width && Terminal Emulator doesn't allow Ctrl+PgUp/PgDown to change the notebook focus.

Tab Width:

Now you can set a fixed width to the tabs so that reallyLongFileNames.txt don't run too wide.

Terminal Emulator:

Similar to not allowing the terminal to override the keyboard shortcuts that change focus from it to something else, I also feel we should allow the notebook the terminal is in to change tabs using Ctrl+PgUp/PageDown

This was something that annoyed me, so I fixed it :-)