[Webtest] [dev] refactoring

[Marc Guillemot]

Hi,

I was asking myself about the utility of some classes:
Setup
TearDown
WebTestSpec
Engine
Context

Indeed
- WebTestSpec just get filled with the information (ie the nested tasks) gathered from WebtestTask (former 
TestSpecificationTask) => what does this artificial separation bring? I can imagine that the idea has been to try 
decouple from ant but as long as all nested steps are ant tasks as well, I don't see the need.
- Engine just executes the steps therefore it's executeSteps should just be a method of WebtestTask
- Setup and TearDown are artificially created steps. I think that their job should be in WebtestTask as well, what would 
allow to reduce the visibility/access of some member variables
- Context just holds informations for the running steps and could be merged in the WebtestTask. Indeed when we need to 
look at the current step number this is the current step number of the webtest rather than of the context of the 
webtest. Same thing for last response.

What do you think?

Notes to the committers:
1- please try not to reinvent the wheel! The Jakarta libs used contain many utility methods that are surely better 
tested as the one we may write ourself. Before writing a new utility, just look if it doesn't already exist
2- please write javadoc to explain your code!
3- mail me if I don't respect the 2 previous points ;-)

Marc.