Use git push mode 'simple'

A new mode for push, "simple", which is a cross between "current" and
"upstream", has been introduced. "git push" without any refspec will
push the current branch out to the same name at the remote repository
only when it is set to track the branch with the same name over there.
The plan is to make this mode the new default value when push.default is
not configured.
Increase dpms screen blank time from 10m to 30m
Add grb's selecta to ~/bin