Add a feature to remove deleted files entries from TM

Summary:
Entries from deleted files are always shown in the Translation Memory. Through an option in the Configuration of the Translation Memory, this feature allows three things :
- Automatically removing the file from the TM when a missing file's entry is opened through the TM tab
- Automatically removing the file from the TM when a missing file's entry is opened through the TM suggestions
- Automatically remove deleted/moved files when rescanning the TM

Test Plan:
  - Delete or move a file within a project and rescan the project
  - Delete or move a file within a project and double click one of its entries in the TM tab
  - Delete or move a file within a project and double click one of its entries in the TM suggestions

Reviewers: aacid, ltoscano, shaforostoff, #localization, mlaurent

Subscribers: mlaurent

Differential Revision: https://phabricator.kde.org/D14069