[#194] dependency cleanup

[bmarwell]

• use less transitive dependencies (tycho-plugins -> tycho-core + sisu-equinox-launching)
• update commons-io to 2.6
• define versions for explicitly and transitively used dependencies
• remove unused dependencies (commons collections)
• remove rarely used dependencies like commons-lang (can easily be replaced).
  • aside from this: using reflection for equals and hashcode is not a good idea.
• added a convergence profile, we will need this again when upgrading tycho.