Remove xwiki-enterprise-archetype module

• it's a pain to maintain something like this, and it's not been maintained for 3 years in practice so it does not have much to do anymore with the current state of XE
• it does not seems to be used at all so it really does not worth the trouble

Some who absolutely wants to create his how distribution of XWiki and for whom creating a flavor is not enough should do the same as XE and use xwiki-platfirm-distribution as parent.

In other work it's not very hard to simply copy/paste XE and modify what you need and there is no point is maintaining something like xwiki-enterprise-archetype given the work and how error prone that is.