Editor / Add support for conditional default view

When creating an editor configuration with more than one default view an exception is returned.

```
Error on line 82 of edit.xsl:
  XPTY0004: A sequence of more than one item is not allowed as the second argument of concat()
```

Instead, select the first default view defined.

Also add support for conditionally defined default views:

```xml
    <view name="default-for-dataset"
          default="true"
          displayIfRecord="count(//dcat:Catalog/dcat:dataset) > 0">
      <tab id="Dataset" default="true">
        <section name="Dataset info"/>
      </tab>
    </view>
    <view name="default-for-service"
          default="true"
          displayIfRecord="count(//dcat:Catalog/dcat:service) > 0">
      <tab id="Service" default="true">
        <section name="Service info"/>
      </tab>
    </view>
```

web/src/main/webapp/xslt/common/base-variables-metadata.xsl

@@ -106,10 +106,11 @@
                         then /root/request/currTab
                         else if (/root/gui/currTab != '')
                         then /root/gui/currTab
-                        else $editorConfig/editor/views/view[@default]/tab[
+                        else ($editorConfig/editor/views/view[@default and
+                          gn-fn-metadata:check-elementandsession-visibility($schema, $metadata, $serviceInfo, @displayIfRecord, @displayIfServiceInfo)]/tab[
                           @default and
                           gn-fn-metadata:check-elementandsession-visibility($schema, $metadata, $serviceInfo, @displayIfRecord, @displayIfServiceInfo)
-                        ]/@id"/>
+                        ]/@id)[1]"/>
 
   <xsl:variable name="viewConfig"
                 select="$editorConfig/editor/views/view[tab/@id = $tab]"/>