abstract the page layout into “layout.tag”

RSS is becoming outdated, JSon is a better example

We were planning to create a ‘help’ but it never happened

Took that opportunity to use custom tag (14 lines versus 2 lines)

 * The old datatables-servlet2 dependency has been removed from the pom.xml
 * Some attributes have been renamed (e.g. paginate => pageable)
 * Starting from the v0.10.0, all web components (servlet, filter) must be explicitely declared in the web.xml file. That's why I added the following declaration: DandelionFilter, DandelionServlet and DatatablesFilter
 * Added a new datatables.properties file in order to disable the asset management brought by Dandelion-Core. This is equivalent to the old cdn=true table attribute

New dependencies added
Old tables replaced by Datatables using Dandelion-Datatables

- integrated Gordon's comments in the POM
- removed antlr from the POM that we don't need anymore
- changed webjars versions inside headTag.jsp

- titles are now aligned
- text color now matches icons color