Configurable tab options

[dandrei]

For compatibility with other ways people use tabs in other programs, the following could be available options, if not defaults:

• Always show tab bar.
• Place the button for adding new tabs immediately to the right of the last tab.
• When colored, the whole tab should have the assigned color.
• Make tabs of equal width, with a sensible minimum width.
• Tabs should be draggable.

[gantryyork]

Tabs should be able to be named/labeled