added allNullOr* and nullOrAll* methods documentation and tests

[rvitaliy]

currently this libs allow call methods like:

Assert::allNullOrString([null, 'string']);
or
Assert::nullOrAllString(null);
Assert::nullOrAllString(['str1', 'str2']);

this PR add test coverage and method documentation to all this methods.

if community approve this PR, I provide to update README.mb and CHANGELOG.mb

[Nyholm]

Thank you for this PR.

It is a bit hard to review with the major diff. And some changes is is just style fixes.

Could you maybe explain why you are doing these 2? 3? different changes and then make them in separate PRs?

[rvitaliy]

@Nyholm ok, i'll split this PR in 2 or 3 punctual PR to make changes clearer

[rvitaliy]

@Nyholm after some investigation i preferred to split in more commits instead of more PR.
let me know if now it is clearer.
I reverted alphabetical order of method documentation to avoid conflicts.

[Nyholm]

I think this looks good.
The diff is quite unfair to you. I had some smaller issues. I will do a final check when they are ready.

[rvitaliy]

@Nyholm [need-help] can't understand why AppVeyor build failed

[Nyholm]

I think AppVeyor is unrelated.