Regular expressions matching
It is proposed to implement an operator matching against a common subset of regular expressions (ECMAScript ones) supported (stdlib (JS, C++, python, PHP) or a separate well-known lib (PCRE for C) ) by every programming language supported by KS.
The operator should accept an expression returning a string and return an array of strings
the first argument is a regex
the second is flags
the third is the string expression to match

The result is an indexable object, which gives access to results (groups) by index. 
```_is_success``` allows to check if the match is succesful.
```_length``` (or what do we have for that) allows to get the length of match results
```to_str``` (or what do we have for that) gives the whole regex matching result
Usage of any groups if there was no success
Look&feel is the following:

```yaml
instances:
  a:
    value: "10:a, b:test ololo"
  parsed:
    value: "regExp('((\w+)\:([ab]|test)(?:, )?)+', 'ig', a)"
    # ["10", "a", "b", "test"]
  is_succesfuly_parsed:
    value: parsed._is_success # true
  whole:
    value: parsed.to_str #10:a, b:test
  length:
    value: parsed._length #4
```