Remove test installation data

This PR removes the testing sample data

# Why?
It is very difficult to maintain AND as we remove what are currently core extensions (eg weblinks) it becomes less useful. I doubt many people other than JBS members ever use it anyway ;)

# B/C
There are no backwards compatibility issues as this only effects new installs

# Language
two language strings are removed and none are changed - I have only done this so far in the en-GB files

# Testing
To test this you can not use com_patchtester as this is for installations. You can download a full installation with this PR applied here
When you install you should no longer see the option to install testing data and it will look like this

![screen shot 2014-09-03 at 12 43 30](https://cloud.githubusercontent.com/assets/1296369/4133512/98ef47e4-335f-11e4-83ba-a840eb998f94.png)