[#1410] Allow setting of log_file_rotate_each.


Problem description
===================

To configure the file log rotation, the following format is used in the configuration file:

```
log_file_rotate_each: 3 days
```

For internal usage, the value is returned as `(3, u'd')` but to update it you need to pass `3 days`

We need to make a uniform format, so the same value that is returned, can also be used for updating.


Why we got into this (5 whys)
=============================

* There was no use case for this as configuration could not be updated at run time.


Changes description
===================

file_rotate_each was updated to allow input value as tuple or list..


How to try and test the changes
===============================

reviewers @alibotean @bnickname 

Check that changes make sense.