LP1081576 - fix utf8 characters in searches using portal page

Replace escape() with encodeURIComponent() on the portal page to allow utf8
characters to be passed more appropriately to the subsequent search in catalog.

Thanks Dan Scott for pointing this out.

Signed-off-by: Ben Shum <bshum@biblio.org>
Signed-off-by: Pasi Kallinen <pasi.kallinen@pttk.fi>