Allow extraction to continue on error

[activescott]

In recent issues where extraction fails on a single file, it is kind of unfortunate that the user cannot keep at least keep some of the files that were extracted successfully and allow the extraction to attempt to continue. So allow the user to choose whether extraction should continue.

Things this enhancement should ensure:

• Prompt the user to allow them to abort or continue extraction.
• Ignore all - Don't force the user to click "continue" on every single file as many may fail. Let them tell the app to ignore all other errors.
• At the end of the extraction, if errors did occur:
  • inform the user again with more detail about what files failed.
  • Encourage them to report the errors to https://github.com/activescott/lessmsi/issues
• Do it in GUI
• Do it in CLI

[activescott]

I started this at #117 but I don't remember where I left off or if it was going in a good direction.