add ability to bulk mark entries as Completed

Feature request for having some UI to select multiple entries, so that can be marked as complete in one go for Qt Linguist tool: 

Please check if it is possible to have something like:
1: Select a context in the "Context"-view and select Complete/Incomplete the whole context.
2: Multi-select in the "Strings"-view and the "Context"-view to be able to select Complete/Incomplete for multiple phrases.