terminal: add dummy terminal implementation

terminal: add dummy terminal implementation

vte: This adds a dummy VTE subsystem. It will be used to emulate a vt100
terminal based on our console subsystem.

terminal: This ties together several subsystems including the output-, the
console- and the vte-subsystem.

The test_terminal test application can be used to test the terminal. It is
supposed to provide a full vt100 implementation which is displayed on all
available screens.

Most of the functionality here is not implemented yet and only a dummy function.
These will be added in later commits.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>