Major refactoring: removing utilities to JAR dependencies

Sigme had many utility classes in package br.com.engenhodesoftware.util
which could be useful to other projects. They were the basis for the
creation of the https://github.com/nemo-ufes/nemo-utils project.

JAR files were generated with Maven from these new projects and placed
in a repository which is used by Sigme to retrieve the dependencies.
Packages were changed to br.ufes.inf.nemo accordingly. The "people"
utility was moved to br.org.feees.sigme instead.