Allow for separate option for the number of read items to appear in main page in the absense of unread items

[cskiadas]

The user should be able to set the following three options:

1. How many items they want on the main page when there are unread items.

2. Whether they want, in that case, for read items to fill the rest of the positions, if there are not enough unread items to fill the above cap.

3. How many items, if any, to show on the main page when there are no unread items. The user should be able to set that equal to 0 or a positive number, or even to -1 if they want this number to be the same as in 1.

[sdcosta]

Outline of what needs to be done http://pastebin.com/463340

[sdcosta]

Fixed by [1086]