Fix Invoice and SalesOrder performance.

There is a private-extensions PR to go along with this:
https://github.com/xtuple/private-extensions/pull/275

This PR should resolve performance issues with XM.Invoice.  A query like this was taking 35-45 seconds:

```sql
select xt.js_init();
select xt.get($${
  "nameSpace":"XM",
  "type":"Invoice",
  "id":"904815",
  "username":"admin",
  "encryptionKey":"xq5j28d19mqp8pvi"
}$$)	
```
After this pull request, it returns in 312ms.

XM.SalesOrder is now fixed as well.  The xt.sochild view has been changed to use the type registration pattern. A query like this was taking 4.5 seconds:

```sql
select xt.js_init();
select xt.get($${
  "nameSpace":"XM",
  "type":"SalesOrder",
  "id":"274793",
  "username":"admin",
  "encryptionKey":"xq5j28d19mqp8pvi"
}$$)	
```
After this pull request, it returns in 828ms.

I do not know what impact removing `salesOrderLine` from here will have on the mobile client

See:

    enyo-client/extensions/source/sales/database/orm/ext/invoice.json