Don't prevent the users from using the ISR if they choose not to block VSFilter like filters.

This commit fixes ticket #4231.
PGS subtitles: Enqueue empty segments to be sure subtitles are properly cleared when using the queue.

This is a work-around and will be improved later.

Refs: #3691.
Update translations from Transifex:

 - Croatian
 - Dutch
 - German
 - Japanese
 - Spanish
 - Ukrainian
 - Vietnamese
Update files for v1.7.5 release.
Update docs/Release.txt.
Set MPC_NIGHTLY_RELEASE to 1.
Translations: Move the language resources to their own file.
Move the UI language selection to the option dialog.

The growing number of translations makes the menu difficult to use.
UI language: Remove the resource IDs.

We don't need resource IDs anymore except to maintain compatibility with the language setting saved from really old versions (nearly two years old). The compatibility gain isn't worth the trouble so people upgrading from those old versions will now have the UI language reset to the default language based on Windows localization.
Subresync bar: Use translatable strings when possible.
Capture dialog: Split some functions and factorize some code.
Fix: The dockable bars were not updated when changing the UI language.
Use the event system to handle UI language changes.
WIP