UAR-784 - Proposal workflow customization [FE KCI-411]

In order to pull in all of the fixes for KC UAR-784, the following two changes were made:
-------------------------------------------------------------------------------
UAR-284 Units dropping from workflow

Added RICE code from KC rice-1.0.3.3:
rice-middleware/impl/src/main/java/org/kuali/rice/kew/rule/FlexRM.java

Modified to contain FE fix, added logic to take into account hierarchy routing such that same level hierarchy route nodes are retained.

-------------------------------------------------------------------------------
UAR-18, Superuser 'return' going to exception

Added RICE code from KC rice-1.0.3.3:
rice-middleware/impl/src/main/java/org/kuali/rice/kew/actions/ReturnToPreviousNodeAction.java

Modified to contain FE fix, added logic to ensure all route nodes are retained in this specific set of conditions.

-------------------------------------------------------------------------------
IMPORTANT: This means local developers will need to build all 3 projects to get this jira's functionality. This also means there will be a pull request on the kc_custom_5.2.1 project. When deploying in our AWS instances, all three projects are built by default, so nothing needs to change there.