Fix build issues on 'master' from DS-2133 fixes

This fixes current build issues on "master" branch, which I accidentally caused by #648 

Does two things:

* Fixes the new profiles added to `[src]/dspace/pom.xml`. Previously, the assembly step was accidentally disabled by default. Now, it is enabled by default, but can be easily disabled by using `-P !assembly`
* Update Travis CI settings to specify `-P !assembly`, which therefore skips building of 'dspace-installer'. Travis will still run all our Unit Tests and build all modules (including those under `[src]/dspace/modules`). It just skips the final creation of the 'dspace-installer' directory.