Filtering with non existing / declared field is ignored

まだ誰も着手していません。

### Bug or feature request

- [x] Bug
- [ ] Feature request

### Description of feature (or steps to reproduce if bug)
1. Insert 10 rows in a model/table
1. Model.find({where: { nonexistingfield: 'test' } })
1. Return 10

### Expected result
Return 0 (Memory connector return 0)
Maybe this should return an error ?

### Actual result (if bug)
Return all the documents/rows

### Additional information (Node.js version, LoopBack version, etc)
Tested with `master` of `loopback-connector-sqlite3`

Start by reproducing the issue with the SQLite3 connector using Model.find({where: { nonexistingfield: 'test' } }) after inserting 10 rows. Compare the result with the stated Memory connector behavior and determine whether an unknown field should return zero rows or an error. Done means the SQLite3 connector no longer returns all rows for this filter, with coverage for the reported query.

索引モデルが issue の本文から書いたものです。