add archived to project, add a list with archived projects
highlight active timespan in overviews
Project dropdown only shows un-archived projects

Also classes are added to archive and un-archive links on the project page.
Merge pull request #228 from DefactoSoftware/jurre/highlight-active-timespan

[READY] highlight active timespan in overviews
Merge pull request #220 from DefactoSoftware/glenn/archive-projects

[READY] add archived to project, add a list with archived projects
Begin billable hours overview