Only set view permission for admin role.
Users have permission to add, edit and delete their entries by default. (closes #108)
Fixed editing of comments, comment type and billable value in timesheet and expenses. (closes #122)
Fixed generating spreadsheet files from the invoice extension. (closes #121)
Fixed wrong warning when deleting expenses. (closes #120)
Removed underscore after edit icon in expenses extension. (#118)
Fixed a lot of PHP warnings. (closes #117 #119)