Previously, the build script was configured to add ajbuilder to the set
of Eclipse/STS build commands, meaning that both javabuilder and
ajbuilder would be present for spring-aspects. This causes unpredictable
behavior, as these two builders compete with each other. As ajbuilder is
a functional superset of javabuilder, this commit ensures that only the
former is present for spring-aspects' .project file.

Also removed warning language in import-into-eclipse.sh about
spring-aspects failing after adding Git support, as this intermittent
problem was almost certainly an artifact of the situation described
above.