fixes #1773

Moved file and path related methods from StringHelper to FileHelper, renamed StringHelper byte methods not to be misused as string methods

as suggested in issue #1316

Fixes #1162: removed constructors of cache dependency classes so that they can be easily created from configuration.

s/value to be cached value/value to be cached/g

Control statements based on the if and elseif constructs must have a single space before the opening parenthesis of the conditional and a single space after the closing parenthesis.

added version information

Zend Data Cache returns null when record doesn't exist (reverted from commit 590121c4)

- 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.

fixes #811

commit in redis branch was:
0cd65e74

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