Require GTK/PyGTK 2.8 instead of 2.6 (means ability to use new cool Glade3 features and new pygtk api)

[nk]

Why:

• foo.set_text('bar') becomes foo.props.text = 'bar' and that's C0000L
• glade3 which is c00000000l reqs 2.8+
• because GTK/Pygtk 2.8 is one year old GTK (PyGTK), that means we can remove some old code about GTK 2.6

I'm more than happy to assist in glade-ing our code, and in rm'ing the legacy code, but I won't do it if you guys think it's too soon (eventhough it is not, because I think .11 will be out in Xmas?)

[dkirov]

Some advantages are that glade-3 supports working with multiple files and

makes files smaller, which influence on less memory usage. The problem is gajim on win32, which is stable only with gtk+2.6. AFAIK (not sure) this gtk version is incompatible with glade-3 generated files.

[nk]

not only that, but glade-3 exposes a lot of properties and attributes

(notably the show_all) which will reduce the code dramatically.

I think that GTK 2.8 (from gladewin32.sf.net) without the win32trayicon is stable enough. Windows users please comment.

[asterix]

this won't add too much for 0.11, let's wait we release it

[nk]

OMG, at last Glade3 uses ONE WINDOW. I bet they finally discovered IDE of 1998

[nk]

(In [7848]) clean code and update to using GTK/PyGTK 2.8; see #2248

[roidelapluie]

note that moving tabs is improved in svn with gtk2.10

[asterix]

only use the no_show_all from glade instead of code remains

[asterix]

(In [8474]) use set_no_show_all from glade when possible instead of code. fixes #2248

[steve-e]

Please update the README.html and comment on http://trac.gajim.org/wiki/DevTools.

Can we no officially use glade-3?

[asterix]

(In [8481]) we now depend on gtk2.8. fixes #2248