Implement a path editor in the Navigation Bar

[josdejong]

Fixes #13

• Implements a path editor where you can see and modify the path, copy, paste, and just type what you want.
• A special copy button on the right side to conveniently copy the path to clipboard
• Throws and error when the path is invalid or does not not exist in the document
• Customizable format: defaults to JSON Path, but you can configure to use for example JSON Pointer instead using the new pathParser option.
• Exports two new util functions: parseJSONPath and stringifyJSONPath

[josdejong]

Published now in v0.7.10