Remove old user interface

Remove old XSLT based interface (admin, main.home, metadata.show, ...).

Identify all XML services API in https://github.com/fxprunayre/core-geonetwork/blob/cleaning/drop-old-ui/web/src/main/webapp/WEB-INF/config/config-service-xml-api.xml. At some point those services will be deprecated.

All new services must be in config folder https://github.com/fxprunayre/core-geonetwork/tree/cleaning/drop-old-ui/web/src/main/webapp/WEB-INF/config and use XSLT in https://github.com/fxprunayre/core-geonetwork/tree/cleaning/drop-old-ui/web/src/main/webapp/xslt.

Also removed all Javascript from the web module as only web-client (Ext.js) and web-ui (Angular) are used now.

Portal services needs a review (https://github.com/fxprunayre/core-geonetwork/blob/cleaning/drop-old-ui/web/src/main/webapp/WEB-INF/config-portal.xml).

Some more work required to completely remove CSS, images, ...