Add Tabbed Document Interface [Feature Request]

[tomlin7]

Tabs allows multiple documents or panels to be contained within a single window, using tabs as a navigational widget for switching between sets of documents.

Add tabs interface to RoboPad.

also, when opening new windows, try to open it in the same window size as the old one. Currently a maximized window appears.
and reduce the opening window's size :)

[roboknight5]

The Tab thing is planned and will be added in a future release and i will see what i can do about the window size thing thank you for your feedback