Document Bingo NoSQL substructure search options

**Steps to Reproduce**
The documentation available for the options passed to Bingo NoSQL substructure search is lacking sufficient detail.

According to the [user manual documentation](https://lifescience.opensource.epam.com/bingo/user-manual-nosql.html#substructure-search):

sub_matcher = bingo_db.searchSub(query, '')

* '' is the matcher options

part:/ is the option for partial search. Example: part:1/5

**Expected behavior**
What does `part:n/m` mean?

**Actual behavior**
Nobody knows.

**Attachments**
n/a

**Additional context**
There doesn't appear to be any way of ranking these options, since the matcher throws an exception on the `getCurrentSimilarityValue()` method.