- LICENSE: change from MIT to AGPL (.Kiss fork)
- Change package name suffix from .Core to .Kiss
(skipping native build)

It seems that these attributes can cause this compilation error in F#4.0:
error FS0927: The kind of the type specified by its attributes does not match the kind implied by its definition

Newer versions of F# (like 4.5 or even newer, like the one being used
by .NETCore to build the binary that is later published in nuget) allow
compiling this code with no issues, but if you reference the generated
assembly later from an old F# compiler, it could generate exceptions at
runtime, e.g.: System.BadFormatImageException (or other types) whose
inner exception could be the following:

System.TypeLoadException : Could not load type of field 'GWallet.Backend.UtxoCoin.Lightning.SerializedChannel:MinSafeDepth@' (6) due to: Expected reference type but got type kind 17

FSharp.Core's Result type is also affected by this so in this commit we
create a replacement for it that is only used in the BouncyCastle build
(which we now rename as 'Portability' build).

Forward-ported from a4a59d0

Co-authored-by: Andres G. Aragoneses <knocte@gmail.com>
Co-authored-by: Andrew Cann <shum@canndrew.org>

This NBitcoin issue: MetacoSA/NBitcoin#931
somehow still hasn't been fixed properly (our geewallet CI still encounters it,
surprisingly).

So let's reapply the workaround[1] that we had removed[2].

[1] joemphilips@d813a97
[2] joemphilips@256893c

ResultUtils: new OptionCE, a computation expression for creating options,
similar to the result computation expression which DNL already has.

Core.Utils: new SeqConsumerCE, a computation expression which makes it
easy to write code which consumes a sequence, one element at a time.

In order to support this, this commit adds two elements:

1) CommitmentToLocalExtension

This is an NBitcoin BuilderExtension that tells
NBitcoin.TransactionBuilder how to recognise and sign to_local txouts
from lightning commitment transactions. This is needed for force-closing
to spend to_local outputs.

2) tryGetFundsFromLocalCommitmentTx

When force-closing a channel this function is used to recover funds from
our commitment transaction. It generates a transaction which can be
broadcast once the timelock on the to_local output has expired.

This function recovers funds from the to_remote output of a remote
commitment tx which has been broadcast to the blockchain.