Bingo NoSQL Substructure matcher does not implement `currentSimValue`

**Steps to Reproduce**

I'm doing a parallel substructure search (across a large corpus split into several individual bingo dbs).
Python 3.x, epam.indigo==1.14.0

```
m = loadQueryMolecule(...)
matcher = db.searchSub(m)
if matcher.next():
id = matcher.getCurrentId()
sim_score = matcher.getCurrentSimilarityValue()
```

**Expected behavior**
Some measure of relevancy should be provided in the score in order to be able to properly sort the results. Sorting by order emitted is not an option since the results must be merged with other result sets.

**Actual behavior**
A "not implemented" error is raised.

**Indigo/Bingo version**
epam.indigo==1.14.0

Start with the Python example using Bingo NoSQL `searchSub`, `getCurrentId`, and `getCurrentSimilarityValue`, then trace the corresponding implementation for `currentSimValue`. Done means parallel substructure searches return a usable similarity score instead of a “not implemented” error, allowing result sets to be sorted and merged.

Written by the indexing model from the issue text.