Fix some bugs with update check type.

-File is a bad default, since it fails for files which are links on linux (and perhaps more).
 Now the default is Timer (which always works, even if it isn't always ideal).
-The type was not saved with the kst file.
-Unpause started another timer each time it was called.  Now it doesn't.

This patch makes no UI string changes, and could be considered for inclusion in 2.0.8
if it hasn't already been released.