Update Vigor Tree

* Fix missing user agent strings on bookmark overlay for AOSP browser

* Add zRam swap to fstab

* Raise persist radio snapshot_timer value

Changes committed:
modified:   overlay/packages/apps/Browser/res/values/liquid_strings.xml
modified:   rootdir/etc/fstab.vigor
modified:   rootdir/etc/init.vigor.rc
modified:   system.prop

Change-Id: I1a103b3026ba92cd8135c1c1db59f50f6c029580