bug #1354 Adding a flag to disable the Monolog error handler (skalpa)

This PR was merged into the 2.0.x-dev branch.

Discussion
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Adding a flag to disable the Monolog error handler

The monolog error handler can now be disabled by setting the value of the new `monolog.use_error_handler` parameter to false (since it was added in  a53ce590 it was always enabled).

The error handler is disabled by default when the application `debug` parameter is set to true, to ensure it won't silence exceptions and/or errors.

Without the flag, an uncaught exception thrown during boot on `master` will just result in a white page, even when using `debug` and `error_reporting` (because the error handler calls `exit` after logging exceptions).

Commits
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8ecd0f01 Adding the monolog.use_error_handler parameter to configure whether the monolog ErrorHandler should be registered.