Webscrapbook

* Fixed an error when a capture is invoked from the context menu of a Firefox private window.
* Fixed an error when a capture is invoked from a private tab in Firefox for Android.
* Fixed an issue that the archive viewer doesn't open additional tabs for a MAFF with multiple web pages in a Firefox private window.
* Adjusted sidebar updating mechanism as a tentative fix for an issue that items get disappeared or misplaced after several move/link/copy operations.

* Fixed an issue that some control chars in a filename causes a downloading error.
* Fixed the bad path rule filler for in-depth capture.
* Fixed an inaccurate error log message for a link with an invalid URL.
* Intermediate data is now cached using indexedDB when available in Firefox.

* Fixed an issue that all tabs are treated as selected when performing a capture or so in a Chromium-based mobile browser.
* Disable drag-and-drop in a Chromium-based mobile browser to prevent an unfixed bug.
* Internal code optimization.

* Fixed an issue that the sidebar scrolling point is reset when the tree refreshes.

* Dropped support of legacy ScrapBook objects. (Use `wsb convert sb2wsb` and `wsb convert migrate` command of PyWebScrapBook to convert pages captured using legacy ScrapBook to WebScrapBook format.)

* Added support of rewriting the `cite` attribute for several elements.
* Added support of handling the `ping` attribute for anchor elements, with a new option `capture.ping` to tweak the behavior.
* Resources used only by inline styles are no more counted as used when `Style images` is `Save used`.
* Added support of `%folder%` and `%path%` formatters for `Copy info` command of the sidebar.