Overhaul bookmarks/chapters

[OpenFunscripter]

This means replacing the current (lazy) implementation.
With a more structured solution.

Bookmarks & Chapters should be exported when saving a *.funscript
This will be the starting point Yoooi0/MultiFunPlayer#72 (comment)

[OpenFunscripter]

Todo

• Serialize bookmarks/chapters to funscript
• Deserialize bookmarks/chapters from funscript
• Reimplement the Export clips functionality

When deserializing requires validation that none of the chapters overlap.

[OpenFunscripter]

chapters/bookmarks are written into and read from the metadata object.

"metadata": {
  "bookmarks": [
	  {
		  "name": "Hello",
		  "time": "02:11:25.273"
	  },
	  {
		  "name": "World",
		  "time": "05:38:13.103"
	  }
  ],
  "chapters": [
	  {
		  "endTime": "00:05:11.839",
		  "name": "A",
		  "startTime": "00:00:00.000"
	  },
	  {
		  "endTime": "00:16:14.735",
		  "name": "B",
		  "startTime": "00:05:11.839"
	  },
	  {
		  "endTime": "00:27:55.654",
		  "name": "C",
		  "startTime": "00:16:14.735"
	  }
  ],
}