Update dependencies

Various dependencies have been updated to their latest versions. The
dependency on aspectjrt has been removed: it's unnecessary to depend
on both rt and weaver as aspectjweaver contains a superset of
aspectjrt. The dependency on cglib has been removed as it was not
being used.
Added additional Gradle properties for SDG dependency version numbers.  Re-organized the dependency declarations in build.gradle and changed version references to use Gradle properties from gradle.properties.