Added PROPFIND Method to Method const in Zend/Http/Request.php

I need this in Project where I implement a WebDav Server with the Zend
Framework 2
Merge branch 'hotfix/3046'

Fix #3046
Close #3296
Merge branch 'master' of git://github.com/julbrygd/zf2 into hotfix/3298
[#3298] Added isPropFind() method

- tests require an is(Method) method for each defined HTTP method constant
Merge branch 'hotfix/3298' into develop

Close #3298