qtconsole : allow copy with shortcut in pager

[Carreau]

closes #1088

[Carreau]

I also added a little fix that avoid some error message when trying qtconsole with --pure as there won't be user_expressionin message comming from the kernel.

Actually I suspect that some of the gui menu of qtconsole might be broken with --pure

[Carreau]

note that we might want to add a warning in the docstring of
console/console_widget.py: def can_copy(self):
Or change the implementation to check wether or not it returns true if selected text is in the pager...

Which way you think is the best ?

[minrk]

@Carreau - you are right, there are probably quite a few things broken in pure mode. I wish we would remove it, because nobody ever tests it, and there are huge amounts of duplicate code that typically are not updated in tandem with every change.

[minrk]

Let's make 'transform_prompt` a widget trait (should be transform_classic_prompt in FrontendWidget, and transform_ipy_prompt in IPythonWidget), then we shouldn't have to override copy() in IPythonWidget at all.

[Carreau]

I'm not quite comfortable with trait , I can give a shot, bu you'll probably be done before I read enough to do it the right way.

[minrk]

Sorry, it can just be a class attribute. The traitness is unimportant.

[minrk]

When doing ipython qtconsole --pylab --paging vsplit, and do plot?, I cannot actually copy anything out of the pager area. So it would appear that this does not do what it claims, unless I am mistaken.

[Carreau]

hum... I didn't thought of vsplit. I'll take a look.

[Carreau]

@minrk,
this seem to work with hsplit/vsplit and without splitter