Clarify the Memento configuration in Openwayback

[aalsum]

Openwayback is supporting memento by default. It depends on enableMemento properties in AccessPoint bean. There is no need for MementoReplay.xml or memento.xml.

The memento configuration should be updated as the following:

1. add enableMemento attributes to the standardsAccesPoint bean to be clear to the administrator how to control the memento.
2. Remove the commented Memento bean from wayback.xml.
3. remove MementoReplay.xml and memento.xml from WEB-INF directory to avoid the confusion.
4. Update the documentation on the wiki to clarify this information.

[ibnesayeed]

Please do so. Recently I was setting up a Wayback instance and it has kept me wondering for several weeks, why is it returning memento headers while I did not enable it?

[ibnesayeed]

I have submitted a pull request #155 that takes care of points 1, 2, and 3. Documentation needs to be updated to clarify this information.