#44 moved the "Page and menus" blog article into the documentation
#44 moved the "Widgets" blog article into the documentation
#22 Renamed guide "Working with Piwik's UI" to "Javascript and CSS"
Fixed case
#44 moved the "Permissions" blog article into the documentation + created a new "Security" category
Merge pull request #48 from piwik/pages

#22 #44 Article reviews and migration