* Currency: Variadic Pairs.Add
This version of Pairs.Add is simpler and [more
performant](https://gist.github.com/gbjk/06a1fc1832d04ee41213ca518938cf74)
Behavioural difference: If there's nothing to add, the same slice is
returned unaltered. This seems like good sauce
* Currency: Variadic Remove
* Common: Add Batch function
* Common: Add common.SortStrings for stringers
* Subscriptions: Add batching to templates
* Subscriptions: Sort list of pairs
* Kucoin: Switch to sub templating
* Kucoin: Simplify channel prefix usage
* Kucoin: Fix race on fetchedFuturesOrderbook
* Subscriptions: Filter AssetPairs
Now only the assetPairs relevant to the subscription are in the context
* Subscriptions: Respect subscription Pairs
* Subscriptions: Trim AssetSeparator early
We want to trim before checking for "AssetSeparator vs All" because a
template should be allowed to reuse a range template and generate just one trailing AssetSeparator
whilst using a specific Asset
* Kucoin: Fix empty margin asset added
* Kucoin: Add Subscription batching
Turns out that contary to the documentation, kucoin supports batching of
all symbols and currencies
* Kucoin: Fix checkSubscriptions and coverage
* Subscriptions: Simplify error checking
This reduces the complexity of error checking to just be "do we get the
correct numbers".
Fixes Asset.All with only one asset erroring on xpandPairs, because we
trimmed the only asset separator, and then errored that we're not
xpanding Assets and the asset on the sub is asset.All
This use-case conflicted with commit 6bbd546d74, which required:
```
Subscriptions: Trim AssetSeparator early
We want to trim before checking for "AssetSeparator vs All" because a
template should be allowed to reuse a range template and generate just one trailing AssetSeparator
whilst using a specific Asset
```
Now we set up the assets earlier, and we remove the check for xpandAssets, since the number of asset lines matching is all that matters.
I've removed the asset tests for this, but they were correctly erroring
on the number of asset lines instead.
Everything hits coverage, as well.
* Kucoin: Remove deprecated fundingBook endpoint
* BTCMarkets: Use common.Batch
* Subscriptions: Add List.AssetPairs
* Subscriptions: Add Template and QualifiedChannel
These fields separate the concept of what the channel is from the
qualified resource name
* Subscriptions: Add List.SetStates()
* Subscriptions: Add List.QualifiedChannels
* Subscriptions: Rename testsubs.EqualLists
* Binance: Switch to ExpandTemplates
* Binance: Update ConfigTest format
* Subscriptions: Test Coverage improvements
* Subscriptions: Reenterant List.ExpandTemplates
* Subscriptions: Move templates from subscriptions to exchanges
* Binance: Inline subscription template and improvements
