Remove BatchResult implementation, remove custom SPL exceptions

[sagikazarmark]

I removed the BatchResult implementation from the main repo, it is going to be in the utility repo.

Some other major changes in this PR:

I removed custom SPL exception extensions.

Reasoning:

The reasons why we have an Exception interface are:

• have a common type for our domain exceptions, since exceptions must extend an Exception class
• allow to catch any exceptions thrown by the adapter

However doing so only make sense when one of the domain exceptions is thrown. For example BatchException. It can be caught by catching the Exception interface. However, exceptions thrown by that BatchException (RuntimeException, UnexpectedValueException) should be handled locally, because they are usually because some sort of logic issue (like getResult called before it is set).

So in this PR I removed all custom SPL exceptions and started to use the core ones. If we ever need more exceptions, like we have now, we can always create new domain exceptions.

What do you think guys?

[sagikazarmark]

There is one question though:

Currently the BatchException only accepts instances of our Exception interface. Should it accept any kind of exceptions? Of course exceptions should be converted to ours if possible, and I can't really imagine any cases where it wouldn't. Still, we should consider this question. (But I rather think we should keep this restriction)

[hannesvdvreken]

:+1: