Cope with $MEMORY_LIMIT not being set

The warning code failed if $MEMORY_LIMIT is not set. Add a guard to
allow it to cope.

[#52692569]
Modify web.xml for auto-reconfiguration

Previously, the auto-reconfiguration JAR was simply copied into the
additional lib directory for any application that had Spring in it.
This did not actually enable any of the auto-reconfiguration
functionality.  This change causes the auto-reconfiguration framework
to modify a /WEB-INF/web.xml file if it exists in the application.
The modifications made by the framework are detailed in the
documentation for it.

[#49695353]
Merge 49695353-modify-web-xml to master

[Completes #49695353]
Merge commit '88c1dbac057abd9b6f8809894ce29d35fae96627'