audio: localizable error string
Add "Copy as text" feature (issue #311)
Lupdate all translations, update Russian translation
Added an option to hide GoldenDict identification in the HTTP User-Agent headers (Issue #259).

A new preference in the "Network" tab is added:
* Do not identify GoldenDict in HTTP headers.
Lupdate all translations
Update Russian translation
Updated Tajik Translation

Updated Tajik Translation
Disable the Scan Pop-up when a Preferences dialog is open