Refactoring of data filtering and data cleanup

* PHP_CodeCoverage_Driver is now an abstract class (was an interface before)
* Move getAllowedLines and getLinesToBeIgnored() from PHP_CodeCoverage to new PHP_CodeCoverage_Parser class
* Move the application of the blacklist/whitelist/"ignored lines" filtering from PHP_CodeCoverage to PHP_CodeCoverage_Driver
* Driver-specific data cleanup is now performed after the blacklist/whitelist/"ignored lines" filtering