facebook: Add support for maps

A new org.gnome.OnlineAccounts.Maps was introduced to denote accounts
that can be used with maps.

https://bugzilla.gnome.org/show_bug.cgi?id=729740
Updated Czech translation
google: Add support for photos

https://bugzilla.gnome.org/show_bug.cgi?id=728877
google: Replace tabs with spaces

https://bugzilla.gnome.org/show_bug.cgi?id=728877
build: Clean up uses of _CFLAGS

Move macro definitions to _CPPFLAGS because they are meant for the
preprocessor and not the compiler.

Fixes: https://bugzilla.gnome.org/729173
telepathy: Silence -Wunused-but-set-variable

... when building without Google or Facebook.

Fixes: https://bugzilla.gnome.org/729173