LP1097928 - Better caps lock message

The TPAC login failure message states "Ensure Caps-Lock is off" however
as was noted on IRC not long ago, passwords are case-sensitive.  So this
message may be misleading.

Signed-off-by: James Fournie <jfournie@sitka.bclibraries.ca>
Signed-off-by: Pasi Kallinen <pasi.kallinen@pttk.fi>
Signed-off-by: Ben Shum <bshum@biblio.org>