Change ctrl+c behavior in ~
Change ctrl+c behavior in ~

While in a continuous build, when the user enters ctrl+c into the sbt
server console (not a thin client connection) when sbt has been launched
in interactive mode, the server exits.  This commit makes it so that
instead we just cancel the watch. As a result, if sbt was started in
batch mode, e.g. `sbt ~compile`, ctrl+c will still exit sbt but in
interactive mode ctrl+c will take the user back to the shell.

xuwei-k/xsbt,mdedetrich/sbt,sbt/sbt,xuwei-k/xsbt,xuwei-k/xsbt,sbt/sbt,mdedetrich/sbt,sbt/sbt,mdedetrich/sbt,mdedetrich/sbt,sbt/sbt,mdedetrich/sbt,mdedetrich/sbt,mdedetrich/sbt,sbt/sbt,xuwei-k/xsbt,sbt/sbt,xuwei-k/xsbt,sbt/sbt