Updates submodule references for REL2.0

Multiple JIRA tickets involved

Previous HEAD position was 5ea03ea... Merge pull request #405 from lukecampbell/pdefs-r2
HEAD is now at ce656e6... Merge pull request #407 from lukecampbell/pdict_update_r2

Previous HEAD position was 03c1495... Merge pull request #122 from ooici/domain-slicing-r2
HEAD is now at 7acf841... Merge pull request #124 from lukecampbell/unlocking-r2