Cache skins and filesystem templates

Attached you'll find a patch that makes use of Velocity cache.

I ran a simple test:

1. Start XWiki
2. Retrieve view/Main [invoked in order to initialize XWiki]
3. Reset timers
4. Retrieve view/Blog - do it 100 times in a sequence (i.e. one at a time)
5. Get request durations from view/XWiki/RequestsStatus

"Retrieve" means I invoke GET URL and then read reponse but I don't parse it and don't make any dependent requests (e.g. for images or Ajax)

HSQLDB

Blog - request #1

Blog - requests #2 - #100

SQLite

Blog - request #1

Blog - requests #2 - #100

Two things to consider:

1. I changed velocimacro.permissions.allow.inline.local.scope to false in order to properly run the blog app (the original one, I didn't upgraded it to 2.0 syntax yet).
   It might be necessary to somehow use the hack with rsvc.parse(source, templateName, false); but actually I'm not sure about it... At the moment I don't understand the difference between setting velocimacro.permissions.allow.inline.local.scope=false and using Da Hack...
2. It might be also good idea to set resource.manager.defaultcache.size=<some number>