- rename FileHelper::mkdir for API consistency
- changed default permission for directories to 775 instead of 777
- added some properties to classes that deal with files to allow control
  over directory permissions.

- cleanup API and usage, add documetation link
- introduced @property feature in getter or setter which has precedence
  over @return or @param tag if present

fixes #811

commit in redis branch was:
0cd65e74

`generateSalt` parameter validation fix.

attribute:type:Header should also affect sort link

correct creation of new Sort object if none is there

use milliseconds only and fall back to seconds for older memcache
versions.

default format is text in short format so it should also be
like that in array() defintion.