New class GeneralDataStream

Added a new class representing the 5250 general data stream.
Do not sent option twice and emit data if not command

TelnetClient does not sent option commands twice and emits data if it is
not a command.
TerminalEmulation and TerminalWidget

New classes TerminalEmulation that parses the general data stream and
informs the TerminalWidget.

The painting of the TerminalWidget is done using a queue of
PainterCommand implementations.

Add first painter command ClearUnitCommand.
Initial version of the cute5250 application