minor performance improvements for insert into

 - avoids new Predicate allocation
 - avoids string join + split to extract contents from a map
move fromMapByPath method into StringObjectMaps
documentation: improve readability; line length, indentation, highlighting.
related pull requests: #1036 #1038 #1043
Merge pull request #1044 from crate/l/improve-docu-readability

documentation: improve readability; line length, indentation, highlighti...
added IndexReferenceInfo to hav a notion if index columns

and forbid match on dynamic references
update changes