Add XWIki Eclipse perspective for working with XWikis

I added an Eclipse perspective containing the XWiki Navigation view, the Outline standard view and the Page Preview view, all for the purpose of having a perspective specially made for editing your XWikis while using XEclipse.
Also, after creating a New Connection using the wizard, if the user is not currently using the XWiki Eclipse perspective, he will be asked to change to it. (Just like when debuging in Eclipse)

This also comes in handy right after installing XEclipse, the user being required merely to change perspective and he is good to go.
Another reason for this perspective is that the 2 provided views don't really go together with other existing perspectives and all the required circumstances for creating a new perspective were met.