Fix encoding of mail headers content-type and content-type-encoding
for single-part mime mails.
Fix spacing
Fix spaces
Fix spaces
Fix spacing
Spaces fixed?
Fix identation (again) + return val
Fix eof_ending + identation change in unchanged code
remove package, subpackage and category

as requested by @samsonasik
Fixes problems highlighted by @DASPRiD and @Maks3w
- do simple in_array comparison for transfer encoding
- remove to many spaces befor equal sign
- use camelCase var names
[mail] Remove unnecessary case insensitive

lowercase and uppercase characters are already included in the range
[mail] Fix assignment to protected methods
[mail] Unify criteria for split fieldname and fieldvalue in the header line.

Also adds @throws tag to interface method docblock.
Remove trailing spaces
[http] Adds docblocks for HeaderInterface interface and methods
[http] Unify criteria for split name and value in header line

Adds a static method in GenericHeader with the responsibility of split both parts.
hotfix 5253
[mail] Fix headers cast to string

Due lazy loading of specific headers is not possible a direct access to the headers attribute.
Instead use the own implementation of ArrayAccess allow lazy load through the get method which do lazy loading of headers.
Merge branch 'Maks3w-hotfix/cs'

Close #5298
Merge branch 'hotfix/mail-proper-cast-headers-tostring' of github.com:Maks3w/zf2 into hotfix/mail-proper-cast-headers-tostring