appDisplay: Use GrabHelper for folder popups

As clicks outside the app picker should still be handled normally
while clicks inside should dismiss the popup, we cannot make full
use of GrabHelper. However using it at least for focus handling
fixes some minor details we are getting wrong, for instance not
restoring the previous focus after dismissing a folder popup.
layout: Do not expand struts to screen edges

set_builtin_struts() in mutter now handles this for us, so we can kill
off the extra code here.

https://bugzilla.gnome.org/show_bug.cgi?id=730527
Updated Spanish translation
messageTray: Don't use a member variable when we can use a local

Tiny cleanup.
messageTray: Remove an unused variable
Mark all gsettings schema entries as translatable

Some entries have untranslatable descriptions/summaries. This means that
when running dconf-editor, some entries will get a translated descriptions,
and a few will not.

https://bugzilla.gnome.org/show_bug.cgi?id=728170
Updated Hebrew translation
appDisplay: Fix app folder "modal-ness"

Commit 5d00c1a5ee moved app folder popups to GrabHelper - for some
reason, the line that ensures the current behavior of only considering
events inside the app picker to dismiss popups got lost ...
viewSelector: use afirmative booleans
appDisplay: Animate folder view items
appDisplay: Use less time to fade in icons than close popup
appDisplay: Animate AllView and FrequentView
appDisplay: Reset to page 0 on end aniamtion
perf: Show apps perf