Refact: preparing for more changes

Splitting low level parsing and high level values extracting
Keys are not a values, which can be referenced
Any value can be referenced by "r" or "R"

"r" - is a value itself - used as link to an object
"R" - is NOT a value - used for PHP's references
Merge branch 'references-upgrade'
Fix: read class name as normal string to handle UNICODE