Toxcore: tidy the API
Add sugar for sendChunk
Use Tox header for all imports, especially enums

Passing Nim enum pointers to the C library was trashing the stack.
Add foreignDeps metadata
Nim 1.0.2 compability, nimpretty
REUSE compliant licensing metadata
Equality operator for index types, its good for tables
A sensible typing status setter
Make FileId an array[32,byte] alias
Use type inference for "send"
Use cstring to avoid unsafeAddr when passing strings to C
Configure options via callback

The options object requires manual memory management, so use a callback
to set options on a managed temporary object during newTox().
Rename File type to FileTransfer
Add hash procedure
Address utilities
Pretty callback setters

Replace the "tox.callbackX = proc (…) = …" with the
prettier "tox.onCallbackX do (…): …" format.
Add README, LICENSE, example
Add IOEffect tags