Refactor the bookmarks to support different data

[lfcnassif]

Currently the bookmark feature can only point to complete case items. It would be useful to support bookmarking hex content snippets, decoded text fragments, doc preview screen shots, timeline events, and also some areas of the analysis app: graph, gallery, map, hits panel, future timeline chart, so on...

[fmpfeifer]

This feature would be a huge improvement for the analysis process.

[lfcnassif]

I'm not going to implement those new types of bookmarks for the future 4.0 release, but I wouldn't like to break compatibility with old 4.x cases bookmarks when this is implemented. I was thinking about inserting some generic Map<String, Serializable> structure into Marcadores(Bookmarks) class to try to make a future implementation backwards compatible. What other devs think?