Fix the cargo default used tomcat container version to explicitly qualified - no longer use 6.0-latest alias

The default Tomcat 6 / 7 version used by cargo is configured in the hippo-cms7-project pom through several properties, including the version which is 'aliased' on 6.0-latest or 7.0-latest.
This alias was resolved through a redirect on our own server (http://apache.hippo.nl/tomcat/) to point to the 'latest' version at Apache (http://archive.apache.org/dist/tomcat/).
This would allow us to 'bump' to a newer version without need for developers to maintain and update the project configuration.
However it now turned out this doesn't properly work, as Cargo 'caches' the container download and only checks if 'a' 6.0-latest / 7.0-latest already is available, and if so never will update it again.

So we've decided to revert to the standard configuration, meaning that we'll now explicitly will provide the 'current' Tomcat container version (and download url) for cargo in the hippo-cms7-project pom, e.g. like this (for CMS 7.9+):

<cargo.tomcat.major.version>7</cargo.tomcat.major.version>
<cargo.tomcat.full.version>7.0.42</cargo.tomcat.full.version>
<cargo.tomcat.distribution.url.prefix>http://archive.apache.org/dist/tomcat/</cargo.tomcat.distribution.url.prefix>
<cargo.tomcat.distribution.url.archive>tomcat-${cargo.tomcat.major.version}/v${cargo.tomcat.full.version}/bin/apache-tomcat-${cargo.tomcat.full.version}</cargo.tomcat.distribution.url.archive>
<cargo.tomcat.distribution.url.postfix>.tar.gz</cargo.tomcat.distribution.url.postfix>
<cargo.tomcat.distribution.url>${cargo.tomcat.distribution.url.prefix}${cargo.tomcat.distribution.url.archive}${cargo.tomcat.distribution.url.postfix}</cargo.tomcat.distribution.url>

resolving to: http://archive.apache.org/dist/tomcat/tomcat-7/v7.0.42/bin/apache-tomcat-7.0.42.tar.gz

For CMS 7.8.5 we will update the hippo-cms7-project pom to point to Tomcat 6.0.37 instead.

Future updates to the hippo-cms7-project pom might update to a newer version of Tomcat, or else this can easily be customized in a custom project extending the hippo-cms7-project by just modifying the tomcat version properties (like above).