Update and refresh template projects

This commit reviews the infrastructure provided by the the war
template projects. The web application can now be easily deployed in
a servlet container with support for the most obvious ones (jetty
and tomcat).

Maven warnings have been fixed and the overall structure of the
build script has been harmonized

The READMEs have been migrated to markdown and the new infrastructure
has been documented.
Polish (template projects)
Update and/or remove gradle settings

Update the gradle settings in the simple project template SPR-0000.

Remove the gradle settings from the SPR-0000-war-* project templates.
The maven pom.xml now offer a wide range of options to run on various
Servlet containers and there is no need to maintain gradle settings
if they don't offer as much. They can be easily added back but will
need to be updated.
Merge pull request #68 from snicoll/infra-update