Custom time frame

Although the daily, weekly, monthly and annually options are OK for the majority of implementations, there are many cases when you are going to need a more granular configuration.

Adding a setting for Custom Time Limit would be nice. A simple way of doing this would simply be using a drop down menu with:

- Minutes
- Hours
- Days
- Weeks
- Months
- Years

Then a number field to type in the limit.

This should count from when the last X nodes was created. If a user has reached the limit then they are blocked, but when the oldest node is older than the time limit, then they can create a new node.