Improvements for the bookmarks user interface

[TheNicker]

This suggestion is partially based on DPack for Visual Studio.

The goal of this suggestion is to use ideas from DPack to have IMHO, a more intuitive and well formed inter-file bookmarking and to extract the replace/allowDuplicates global setting from #6 to a per bookmark runtime property.
I believe this suggestion covers more use cases than those that are currently available.

Definitions:

• Bookmark / local bookmark - per file and shouldn't affect any other file in the workspace:
• Global bookmark - per workspace, shared among all files
• Cyclable bookmark - an entry in a Bookmark group . similar to the 'allowDuplicates' from Single numbering system across files #6, can be used both for local and global bookmarks
• Bookmark group - a set of Cyclable bookmarks.

Usage:

• Toggle a local bookmark - Ctrl + Shift + [Number]
• Toggle a global bookmark - Ctrl + Shift + Alt + [Number]
• Toggle a cyclable bookmark, local or global - Ctrl + Shift + [Number] + [Number] and Ctrl + Shift + Alt + [Number] + [Number] respectively.
• Navigate/ cycle through a local bookmark - Ctrl + [Number]
• Navigate/ cycle through a Global bookmark - Ctrl + Alt + [Number]

Setting a non-cyclable bookmark over a bookmark group, overrides the bookmark group.
Re-Setting a cyclable bookmark adds it to the last assigned bookmark group.

Visualization

There are 4 different types of bookmarks local/local cyclable/global/global cyclable.

For a clear recognition, different glyphs and/or colors should be used to distinguish local bookmark and global bookmark. the same for Cyclable and non-Cyclable bookmark.