Parser for annotated BNF (ANBNF) grammar

[jenetics]

The extended Cfgobject created in issue #889 allows to add annotations. In this ticket, the BNF format should be extended such that it is possible to such annotations in a BNF string.

Example

<expr> ::= <num> | <var> @weight=4 | '(' <expr> <op> <expr> ')' @weight=5
<op>   ::= + | - | * | /
<var>  ::= x | y
<num>  ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9