Document the Transfer subcomponent

[weierophinney]

Currently, the Transfer subcomponent, which provides facilities around managing file uploads and reporting file upload progress, has no written documentation, and needs some.

There is, however, documentation for the ZF1 equivalent, starting with:

• http://framework.zend.com/manual/1.12/en/zend.file.transfer.introduction.html

I recommend whoever takes this on:

• Converts the docbook sources from ZF1 to markdown.
• Updates the markdown sources to refer to the ZF2 namespaces and class names.
• Reviews the code to determine if the documentation matches actual capabilities, updating as required.

[weierophinney]

Closing. Zend\File\Transfer is essentially deprecated by the zend-filter and zend-validator File subcomponents, and the FileInput functionality of zend-inputfilter.