A number of small changes to make the GUI more obvious.
"Next" buttons for during character creation.
A "Level Up" button on the skill screen.
A "Done" button when editing a Culture.
"New Item" and "Delete Item" buttons in addition to the right-click menu.
Added some keyboard shortcuts.
Ctrl-N,O,S will do File->New, File->Open, and File->Save
Ctrl-Tab and Ctrl-Shift-Tab will cycle through the tabs.
Ctrl-Number will jump to a tab.
Closes #7