View source for Multiple Window Support

==== Multiple Window Support====

(this part is all done)

previously Bluefish had always just one active document. Because there was only one window, it was simply the
document visible in that window. All bluefish functions could simply act on main''v->current''document.

Now there will be more windows, so many functions need to pass their window in the arguments (Tbfwin*) so they know
which document (Tdocument* in bfwin->current_document) they have to act on.

Also some files used local variables because there was anyway no need to have multiple windows available (the search
and replace dialog for example). But now with multiple window support there might be multiple search and replace windowa
active. I think that goed for all dialogs except the preferences dialog.

So basically 50% of the API has to change (adding a Tbfwin *bfwin) in many of the files..

==== Projects and windows in the menu====

since projects always have their own window, we'll discuss this here:

where should those menu items go

/Project/... ?
or /File/Project/... ?

/Window/... ?
or something else ?

*Olivier votes for: /Project/ and /Window/
* Alastair thinks that...:
''''''Project related stuff should go in /project/
'''''' window related stuff (new, close) should go in window.
'''''' The Options menu could be split up. Put the prefs related things in /Edit/ menu, and the the other ones would fit fine in the /window/ menu??