Fix custom labels not saving settings properly

[dsafa]

Summary

Text labels were not writing the changes back to application settings.

Checklist

• Tests passed
• Changes validated (manually or automated)
• Closes / Fixes Text positioning resets to default on explorer.exe restart, or computer reboot #206 (if applicable)

Additional details / comments

OnEndEdit was not being overridden properly to write the values back to the source. Additionally fixed removing labels not publishing an edit start message.

Manual test steps (if applicable)

1. Edit custom label position.
2. Press apply.
3. Reset explorer
4. Observe that the values have been saved properly.