Removing Zend_Registry from Core

fixes #4188

Refactoring the code so that base.css is not required to be manually built but is compiled on each page view which should be fast enough

Updating readme with instructions to chmod 777 the tmp/ directories when running phpunit tests suite on dev
+ adding tmp/logs to directories that are automatically created

Conflicts:
	core/ErrorHandler.php
	core/ExceptionHandler.php
	core/FrontController.php
	core/Log.php
	core/Piwik.php

Rewrite logging in Piwik and remove Zend_Log
goal: logging easily reusable by plugin developers. The next step will be to allow developers to easily view the logs, Log Viewer UI is in http://dev.piwik.org/trac/ticket/2473 (would be useful to view eg. archive.php frequency&exec times)