orblogin: Less magic numbers, smaller login button

Make Orbital Login Window Unclosable (calc, editor, file mgn, orblogin)

made a new function in orbtk, Window::new_flags if need to make a
window with flags

Added &[WindowFlag::Exit] to call to window which creates login. In
other programs, if not flags were previously pass I now pass &[]

Use mime_guess in file manager

Implemented the open functionality for editor

browser: Parse content-type header

This fixes some websites that send character encoding information in the content-type header

file_manager on orbtk

Use hyper in browser

Scrolling feature added to file manager

Fixed scroll not resetting after changing directories.
Fixed selecting after scroll picking files/dirs as if offset was at 0.

When there are more files than certain limit (set to 7),
the file manager will not display more than 7 files and displays
two buttons that scrolls down/up (scrolls by 2 when possible,
scrolls by 1 instead if possible, otherwise doesn't scroll at end).