Implement deletion and undeletion in ndsc

Use 'x' to delete the selected transaction and 'u' to undelete
previously deleted transactions (in same ndsc session).
Implement Vim-style keybindings in ndsc

This allows navigating more easily and delete and undo multiple things
at once.
Handle exception properly
Implement the refresh command

This command fetches the new transactions from the discuss server.
Release discuss-ng 1.1
Merge 1.1 release into Debathena
Release 1.1 in Debathena