Bugfix LDAP config to play nice with Zebra.

Bugfix LDAP config to play nice with Zebra.

The section in KOHA_CONF was moved inside <config> and renamed
<ldapserver>.  Perldoc updated to correspond.  Tested with local
LDAP and existing test (t/db_dependent/Auth_with_ldap.t).
Patch can be applied with confidence based on comparison of 2 dumps:
perl -e 'use C4::Context; use Data::Dumper; my $context=C4::Context->new("./old_config.xml"); print Dumper ($context->{server}->{ldapserver}),"\n";'
 and
perl -e 'use C4::Context; use Data::Dumper; my $context=C4::Context->new("./new_config.xml"); print Dumper (C4::Context->config("ldapserver")),"\n";'
These dumps reflect the way Auth_with_ldap accesses configuration info before and after.

Signed-off-by: Joshua Ferraro <jmf@liblime.com>