Add ipython configuration (as own subvault)

And since we provide subvaults file, we have to specify also those that
would be normally default.

dotfiles/dotvault/subvaults

@@ -0,0 +1,2 @@
+ipython/profile_default
+config

dotfiles/ipython/profile_default/ipython_config.py

@@ -0,0 +1,2 @@
+c.TerminalInteractiveShell.confirm_exit = False
+c.TerminalInteractiveShell.display_completions = 'readlinelike'