add some post login scripts/programs to awesome rc

- run xscreensaver daemon
- run screenlock.sh to lock screen every X minutes.
add screenlock scripts

- screenlock.sh takes an argument and locks screen after this many
  minutes
- runScreenlock.sh adds a GUI on top of this
give minutes arg to screenlock.sh in awesome/rc.lua

make screenlock.sh sleep for 25 mins before locking screen, i.e. lock
screen every 25 mins to enforce thesis writing breaks