More efficient flat file list format and various UX improvements (#3)

This is a major upgrade with assorted things included.

- Navigation flows improved, search appears in URL history, cleared when navigating to another folder
- More efficient file list format for faster loads
- Efficient updates, never re-send full root another time (except at connection)
- Large number of watching and filelist updates (inotify issues remain)
- File size coloring
- Fixed ZIP generation random glitches (thread race condition)
- Code refactoring, cleanup, typing fixes
- More tests

Reviewed-on: #3

cista/api.py

@@ -104,11 +104,11 @@ async def watch(req, ws):
     )
     uuid = token_bytes(16)
     try:
-        with watching.tree_lock:
+        with watching.state.lock:
             q = watching.pubsub[uuid] = asyncio.Queue()
             # Init with disk usage and full tree
-            await ws.send(watching.format_du())
-            await ws.send(watching.format_tree())
+            await ws.send(watching.format_space(watching.state.space))
+            await ws.send(watching.format_root(watching.state.root))
         # Send updates
         while True:
             await ws.send(await q.get())