MainWindow Refactor Part 4 of 5

Split the views in MainWindow into separate classes;

* Tab is a collection of the 4 main views

* TabView is a base class for all of the 4 view types

* {Analysis,Train,Diary,Home}View are all derived from
  TabView and deal with specifics of those views (e.g.
  Diary/Home worry about date ranges).

We should be ready to move to tabbed athletes soon.

There are a few nits left for this part of the refactor
that will need to be resolved in some fixups over the
next few days;

* tile mode segment selector has wrong segment selected
  when the view is in tile mode.

* Minimum height/width of MainWindow is large for some
  reason

* the Train view controls (play, ffwd etc) have nowhere
  to go at present -- need to fix that !!!

* When you resize the mainwindow width the sidebars expand
  and should remain a fixed width

* not sure if it will build on Windows or Mac!