Drop dependency on zendframework/zend-loader

[michalbundyra]

This removes the dependency on the zendframework/zend-load package, as suggested in #185

The HeaderLoader class has been removed and replaced by a simple class map in the Headers class.

However, I have also removed the getPluginClassLoader and setPluginClassLoader methods. Since they are public, this might be a BC break. What do you think?

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Originally posted by @acelaya at zendframework/zend-mail#186

[michalbundyra]

Builds are failing with latest dependencies, but they are failing in master too.

I'll try to figure out how to fix them, but it might take me time.

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Originally posted by @acelaya at zendframework/zend-mail#186 (comment)

[michalbundyra]

Please rebase onto develop

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Originally posted by @Xerkus at zendframework/zend-mail#186 (comment)

[michalbundyra]

There is a PR with fix, I will merge it shortly

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Originally posted by @Xerkus at zendframework/zend-mail#186 (comment)

[michalbundyra]

Perfect then. Thanks.

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Originally posted by @acelaya at zendframework/zend-mail#186 (comment)

[michalbundyra]

I have rebased develop. I'll do it again once you merge the other PR.

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Originally posted by @acelaya at zendframework/zend-mail#186 (comment)

[michalbundyra]

Just a heads up: there is a big ongoing effort going for next major versions for zend-expressive and related packages as well as for zend-mvc. This change will require a next major version, and I do not expect to get to it until february.

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Originally posted by @Xerkus at zendframework/zend-mail#186 (comment)

[michalbundyra]

Ok, no rush :-)

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Originally posted by @acelaya at zendframework/zend-mail#186 (comment)

[michalbundyra]

This repository has been moved to laminas/laminas-mail. If you feel that this patch is still relevant, please re-open against that repository, and reference this issue. To re-open, we suggest the following workflow:

• Squash all commits in your branch (git rebase -i origin/{branch})
• Make a note of all changed files (`git diff --name-only origin/{branch}...HEAD
• Run the laminas/laminas-migration tool on the code.
• Clone laminas/laminas-mail to another directory.
• Copy the files from the second bullet point to the clone of laminas/laminas-mail.
• In your clone of laminas/laminas-mail, commit the files, push to your fork, and open the new PR.
  We will be providing tooling via laminas/laminas-migration soon to help automate the process.

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Originally posted by @weierophinney at zendframework/zend-mail#186 (comment)

[samsonasik]

I've created PR #95 for it.