DMN11 — extra level of indirection in decision table serialization is undesirable

The input and output entries in a decision table are expressions. The expressions are serialized as part of the rule 'clause', with an ID. In the rules, the expressions are represented by IDREF. This level of indirection is undesirable for many reasons:
1. the expressions are small text strings, typically no bigger than an ID
2. copy/paste of rules across decision tables won't work (IDs are different)
3. diff of decision tables is complicated, due to indirection
4. there is no level of indirection in the notation - the rules appear to contain the expressions, not a reference to them.
5. complicates JSON serialization
Proposed: In Figure 44, move Expression ownership from Clause to DecisionRule, and follow logical implications in text and xsd.

remove indirection, split Expression into LiteralExpression and UnaryTests

DecisionRules are ordered in a DecisionTable. By also ordering the inputs and the outputs (requires splitting Clause into InputClause and OutputClause, we can move the inputEntries and outputEntries under DecisionRule and avoid all IDREFs within a decision table, significantly simplifying serialization. Also, we combine a proposal for DMN11-84, which is merged with this issue.