multi: build with eth code by default

[chappjc]

This negates the lgpl build tag, making it nolgpl.

The importlgpl.go files in the CLI app (main) packages are updated to indicate that the nolgpl build tag should be used to exclude such code if it is not acceptable.

Use of any of the eth-specific packages now implies lgpl. That is, we gate at the import of these packages in the cmd apps that would use them via their importlgpl.go files that require the !nolgpl build tag.

All docs and scripts are updated for the new default.

[chappjc]

client/cmd/dexc:

$ go build -tags nolgpl && go version -m . | grep ethereum
$ go build && go version -m . | grep ethereum
	dep	github.com/ethereum/go-ethereum	v1.10.25	h1:5dFrKJDnYf8L6/5o42abCE6a9yJm9cs4EJVRyYMr55s=
$ 

[martonp]

Why aren't you putting!nolgpl in all the eth files? Was that just never needed?

[chappjc]

Why aren't you putting!nolgpl in all the eth files?

Use of any of the eth-specific packages now implies lgpl. That is, we gate at the import of these packages in the cmd apps that would use them via their importlgpl.go files that require the !nolgpl build tag.

Seems reasonable since if you import the packages explicitly. There's a doc.go in each of those that basically states "by using this package use are using LGPL code"

But yeah, maybe this was all unneeded in the first place.

[chappjc]

The other unfortunate thing I noticed is that if you use the gopkg.dev docs page (https://pkg.go.dev/decred.org/dcrdex), it does not even show the packages with no default-built code. I think it should show it all (with this PR), and the doc.go explains the license of that package.