Last-Modified method returns current time

[NotBobTheBuilder]

The Last-Modified HTTP header is always set to the current time, regardless of when it was previously set.

I think the problem is occuring here in classes/Base/Response, it looks like the last modified time is, for some reason, null.

I think it would be worth extending the code here so that in the case of no Last Modified time being found, the value of strtotime('now') is persisted in the lastModifiedTime property and saved to the DB.

[NotBobTheBuilder]

Presumably, the getLastModified method should do the following:

• In the case of an Object, return the value of the lastChange field
• In the case of a Collection, return the most recent value of lastChange within its Objects

[JonTheNiceGuy]

I think that was the plan, I just failed to implement it. :(