[under review] assortment of improvements

[tarzan]

• [ ] reports -> select client -> does not filter projects
• [ ] total number of hours in report overview -> #298 also add maybe on billables-route?
• [ ] clients overview -> select one, should only show unarchived/active projects
• [ ] on billables -> add total of currently selected entries
• [ ] in reports, clicking on columns sorts it by that type
• [ ] export of report has different number of columns for milages vs hours