Show only active tasks in the invoice select form

If there are tasks with an hourly rate that have no time entries,
then it's not worth showing them.
Add in_current_month? method to the TimeEntry model
Only select time entries that are not in the current month
Merge branch 'feature/ff83ce-preselect-time-entries-invoice-form' into development (closes: #ff83ce)
Bump version to 1.10
Update the changelog for the new release
Merge branch 'release/1.10'
Merge tag 'v1.10' into development

Release 1.10