Nested tags and contexts

[larralapid]

Allow for nesting tags and contexts by detecting character like ">" or "/"

---

TODO:

• Parse project/tag/context by special symbol \
• ??? Create a decoration in editor painting \ in different color ???
• Editor autocomplete must have another trigger character \ and different autocomplete items
• Filter must search by part of the nested item
• Webview must render nested items differently
• Webview clicking on item should support clicking on part of the nested item to filter

[usernamehw]

Currently, even projects have no nested features. They are all treated the same way:

Project/tag/context can have any non-whitespace symbol in them.