Change default tabs position to left

This should users get accustomed to the UI changes we plan for 1.3

Also it hides the problems with the not scrollable tabs list because much more tabs fit the window

gajim/common/config.py

@@ -170,7 +170,7 @@ class Config:
         'last_save_dir': [opt_str, ''],
         'last_send_dir': [opt_str, ''],
         'last_sounds_dir': [opt_str, ''],
-        'tabs_position': [opt_str, 'top'],
+        'tabs_position': [opt_str, 'left'],
         'tabs_always_visible': [opt_bool, False, _('Show tab when only one conversation?')],
         'tabs_border': [opt_bool, False, _('Show tabbed notebook border in chat windows?')],
         'tabs_close_button': [opt_bool, True, _('Show close button in tab?')],