Delete all release POM templates in 'build'

Delete all release POM templates in 'build'

In order to keep developers from creating AspectJ releases manually or
using Ant script 'build/build.xml', get rid of all POM templates. This
step does not involve updating any build or release how-to documents or
any other clean-up work under 'build', but it is a first step and a
simple, implicit reminder that now we can build and release using Maven.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>