Better support for repeated model bindings in template

[dselman]

It is common for templates to include multiple references to the same template model property. At the moment the first reference is used to bind to the model, all others are ignored. We should at least validate that all references are equivalent and flag an error for inconsistent bindings.

See the code here:
https://github.com/accordproject/cicero/blob/master/packages/cicero-core/lib/template.js#L304

[jeromesimeon]

This issue is fixed using the new parser infrastructure. Here is an example:

bash-3.2$ cat text/sample.md 
## Acceptance of Delivery.

"Party A" will be deemed to have completed its delivery obligations
if in "Party B"'s opinion, the "Widgets" satisfies the
Acceptance Criteria, and "Party B" notifies "Party A" in writing
that it is accepting the "Widgets".

## Inspection and Notice.

"Party B" will have 10 Business Days to inspect and
evaluate the "Widgets" on the delivery date before notifying
"Party A" that it is either accepting or rejecting the
"Widgets".

## Acceptance Criteria.

The "Acceptance Criteria" are the specifications the "Widgets"
must meet for the "Party A" to comply with its requirements and
obligations under this agreement, detailed in "Attachment X", attached
bash-3.2$ ~/git/cicero/packages/cicero-cli/index.js parse 
8:59:18 AM - info: Using current directory as template folder
8:59:18 AM - info: Loading a default text/sample.md file.
8:59:20 AM - info:
{
  "$class": "org.accordproject.acceptanceofdelivery.AcceptanceOfDeliveryClause",
  "shipper": "resource:org.accordproject.organization.Organization#Party%20A",
  "receiver": "resource:org.accordproject.organization.Organization#Party%20B",
  "deliverable": "Widgets",
  "businessDays": 10,
  "attachment": "Attachment X",
  "clauseId": "f4ecdf18-60ef-4758-aace-50b9feed7f2e"
}
bash-3.2$ cat text/sample.md 
## Acceptance of Delivery.

"Party XXX" will be deemed to have completed its delivery obligations
if in "Party B"'s opinion, the "Widgets" satisfies the
Acceptance Criteria, and "Party B" notifies "Party A" in writing
that it is accepting the "Widgets".

## Inspection and Notice.

"Party B" will have 10 Business Days to inspect and
evaluate the "Widgets" on the delivery date before notifying
"Party A" that it is either accepting or rejecting the
"Widgets".

## Acceptance Criteria.

The "Acceptance Criteria" are the specifications the "Widgets"
must meet for the "Party A" to comply with its requirements and
obligations under this agreement, detailed in "Attachment X", attached
bash-3.2$ ~/git/cicero/packages/cicero-cli/index.js parse 
8:59:42 AM - info: Using current directory as template folder
8:59:42 AM - info: Loading a default text/sample.md file.
8:59:45 AM - error: Inconsistent values for variable shipper: Party XXX and Party A
Error: Inconsistent values for variable shipper: Party XXX and Party A
    at mkCompoundVariable (/Users/jeromesimeon/git/cicero/node_modules/@accordproject/markdown-template/lib/combinators.js:79:23)
    at mkClause (/Users/jeromesimeon/git/cicero/node_modules/@accordproject/markdown-template/lib/combinators.js:143:12)
    at /Users/jeromesimeon/git/cicero/node_modules/@accordproject/markdown-template/lib/combinators.js:340:16
    at Parsimmon._ (/Users/jeromesimeon/git/cicero/node_modules/parsimmon/src/parsimmon.js:989:51)
    at Parsimmon._ (/Users/jeromesimeon/git/cicero/node_modules/parsimmon/src/parsimmon.js:685:40)
    at Parsimmon._ (/Users/jeromesimeon/git/cicero/node_modules/parsimmon/src/parsimmon.js:985:23)
    at Parsimmon._ (/Users/jeromesimeon/git/cicero/node_modules/parsimmon/src/parsimmon.js:985:23)
    at Parsimmon.<anonymous> (/Users/jeromesimeon/git/cicero/node_modules/parsimmon/src/parsimmon.js:1252:19)
    at Parsimmon._ (/Users/jeromesimeon/git/cicero/node_modules/parsimmon/src/parsimmon.js:685:40)
    at Parsimmon._ (/Users/jeromesimeon/git/cicero/node_modules/parsimmon/src/parsimmon.js:985:23)