Optimize PdfParser::readValue()

[JanSlabon]

The current readValue() method shall be made private and renamed to readValueByToken($token, $expectedType).

Implement a new readValue() method which will have an optional parameter $expectedType.
Internally it will resolve the first token and forward it to the new private method. It also will forward the $expectedType accordingly.

The checks for the $expectedType have to implemented accordingly.

Code that calls readValue() needs to be optimized to use the $expectedType.

This optimization allows better error handling in faulty PDF files.