Remove the static title setting from profile preferences

The static title setting does not work because TerminalWindow hardcodes
the title as "Terminal" in the absence of VteTerminal:window-title,
which is set dynamically via escape sequences. Usually the escape
sequence is emitted from a suitable PROMPT_COMMAND. You can do the same
if you want a customized title.

https://bugzilla.gnome.org/show_bug.cgi?id=724110
screen: Remove unused description and user_title API

These were used by various parts of the static title code, which has
now been removed.

https://bugzilla.gnome.org/show_bug.cgi?id=724110