NetworkAgent: handle empty hints and VPN secrets correctly

get_secrets_keyring_cb() contained an optimization (copied over from
nm-applet) that avoided a D-Bus round-trip when NetworkManager sent
secrets hints that were not satisified by the user.  This code did
not properly handle empty hints though, and proceeded to always
request new secrets whenever empty hints were sent.  Remove this
code entirely since the complexity is not worth it (per Jasper).

Second, get_secrets_keyring_cb() was mishandling VPN secrets which
were marked as "always ask".  Because the VPN secrets are not GObject
properties because they cannot be pre-defined, they are passed in
a hash table that is a GObject property marked 'secret'.  Unfortunately,
that means that the shell agent cannot determine their secret flags.
But since the VPN plugin auth dialogs have much better information
about what's required than the shell agent does, always ask the VPN
auth dialogs to handle the secrets requests after grabbing any that
already exist from the keyring.  This is also what nm-applet does.

https://bugzilla.gnome.org/show_bug.cgi?id=719815
runDialog: Explicitly set horizontal alignment

When set to fill, the label will always end up left-aligned, which
is only correct in LTR locales. Set the alignment explicitly to
work in both RTL and LTR locales.

https://bugzilla.gnome.org/show_bug.cgi?id=712579
js: Use SOURCE_CONTINUE/SOURCE_REMOVE constants in source functions

With support for boolean constants in g-i, we can finally use the
more readable constants instead of true/false.

https://bugzilla.gnome.org/show_bug.cgi?id=719567
js: Use EVENT_PROPAGATE/EVENT_STOP constants in event handlers

Just as SOURCE_CONTINUE/SOURCE_REMOVE in source functions, these
constants increase code clarity over plain true/false.

https://bugzilla.gnome.org/show_bug.cgi?id=719567
calendar: Don't ever force reload

https://bugzilla.gnome.org/show_bug.cgi?id=720298
calendar: Don't rebuild the entire calendar widget when choosing a date

It's inefficient and wasteful. Combined with the JS GC not being great,
it leaks around 100 actors waiting to be GC'd. Yikes.

https://bugzilla.gnome.org/show_bug.cgi?id=720298
Remove use of superfluous MetaWindowActor APIs
Updated Galician translations
Tajik translation updated
Updated Spanish translation
Bump version to 3.11.3

Update NEWS.
Updated slovak translation
Update Chinese simplified translation
Updated German translation
Updated Slovenian translation
Updated Aragonese translation
Updated Norwegian bokmål translation
[l10n] Updated Italian translation.
ShellAppSystem: own the memory for the startup wm class and app id

The hash table must keep a copy of the IDs, because the GAppInfos
are unreferenced (and thus freed) at the end of the function.
This was possibly not a problem if the GAppInfos were referencing
the memory-mapped cache, but it becomes one for regularly parsed
desktop files in ~/.local.

https://bugzilla.gnome.org/show_bug.cgi?id=721039
Updated Brazilian Portuguese translation