Bug 10405: add IDs for custom regions

This patch adds unique IDs for:
opaccredits
opacheader
OPACMobileUserCSS
OpacNavBottom
OpacUserCSS
opacuserjs

This is most useful for previewing changes you make in the OPAC
preferences using the following javascript in your IntranetUserJS:

function showPreview(url) {
    document.getElementById('opac-preview').src = url;
    $('#opac-preview').load(function () {
        $('#opac-preview').show();
        $('#region-opaccredits', $('#opac-preview').contents()).html($('#pref_opaccredits').val());
        $('#region-opacheader', $('#opac-preview').contents()).html($('#pref_opacheader').val());
        $('#opacmainuserblock', $('#opac-preview').contents()).html($('#pref_OpacMainUserBlock').val());
        $('#opacmainuserblockmobile', $('#opac-preview').contents()).html($('#pref_OpacMainUserBlockMobile').val());
        $('#region-opacnav', $('#opac-preview').contents()).html($('#pref_OpacNav').val());
        $('#region-opacnavbottom', $('#opac-preview').contents()).html($('#pref_OpacNavBottom').val());
        $('#opacrightsidebar', $('#opac-preview').contents()).html($('#pref_OpacNavRight').val());
        $('#noresultsfound', $('#opac-preview').contents()).html($('#pref_OPACNoResultsFound').val());
        $('#opacresultssidebar', $('#opac-preview').contents()).html($('#pref_OPACResultsSidebar').val());
        $('#region-opacusercss', $('#opac-preview').contents()).replaceWith('<style id="region-opacusercss" type="text/css">' + $('#pref_OPACUserCSS').val() + '</style>');

        $('#region-opacuserjs', $('#opac-preview').contents()).replaceWith('<script id="region-opacuserjs" type="text/javascript">' + $('#pref_opacuserjs').val() + '</script>');
    });
}

$(document).ready(function () {
    if ($('#pref_OpacNav').size() > 0) {
        $('#doc3').after('<div class="navbar navbar-fixed-bottom" style="z-index: 10000;"><div id="preview-pane" class="navbar-inner"><h4 style="float: left; margin-right: 2em;">Preview changes</h4><div class="btn-group" data-toggle="buttons-radio"><button type="button" class="btn" id="preview-main">Main page</button><button type="button" class="btn" id="preview-results">Results</button><button type="button" class="btn" id="preview-details">Details</button><button type="button" class="btn active" id="preview-hide">Hide</button></div><iframe id="opac-preview" style="height: 20em; width: 100%; display: none;"></iframe></div></div>');

        $('#preview-main').click(function () {
            showPreview('/cgi-bin/koha/opac/opac-main.pl');
        });
        $('#preview-results').click(function () {
            showPreview('/cgi-bin/koha/opac/opac-search.pl?idx=&q=pqf%3D%40attr+1%3D_ALLRECORDS+%40attr+2%3D103+%22%22&branch_group_limit=');
        });
        $('#preview-details').click(function () {
            showPreview('/cgi-bin/koha/opac/opac-detail.pl?biblionumber=1');
        });
        $('#preview-hide').click(function () {
            $('#opac-preview').hide();
        });
    }
});