ErrorHandler: enhanced customizable error handler implementation

This class is a powerful wrapper for PHP error-reporting features. It helps when developing new scripts and monitoring sites in production state, too.

It has several enhancements (previously known as report layouts):

* SOURCE = prints the source code fragment where the error encountered,

* CONTEXT = prints variable context around error source,

* SILENT mode = suppresses error-messages

* REPLACE page = displays an arbitrary HTML or PHP page in case of error (useful in production state),

* LOGGING = log errormessages wherever you want (multiple destination also allowed),

* Autodetecting Target Logging = log target can vary from file to file automatically

* CONSOLE window = error messages will be displayed in a separate browser window not to break up your pretty page design

* Error TRAPPING = catching errors for runtime generated codes


Each report can be enabled, disabled or changed at run-time.