libview: Update the caret cursor when jumping to a find result

https://bugzilla.gnome.org/show_bug.cgi?id=728996
libview: Be sure we have an EvViewAccessible before setting its page range
Use thumbnails as default sidebar page

When the sidebar page set by the document metadata
is not supported, it falls back to thumbnails.

https://bugzilla.gnome.org/show_bug.cgi?id=628617
sidebar: Enable supported pages after reloading

When a document is reloaded, the supported pages
in the sidebar should be enabled.

https://bugzilla.gnome.org/show_bug.cgi?id=628617
sidebar: select correct page after reloading

Once a document is reloaded, if the current
sidebar page is no longer supported, it should
change to the first supported page. Otherwise, it
does not change pages.

https://bugzilla.gnome.org/show_bug.cgi?id=628617