* Allow commands to return a Task<RuntimeResult>
This allows bot developers to centralize command result logic by
using result data whether the command as successful or not.
Example usage:
```csharp
var _result = await Commands.ExecuteAsync(context, argPos);
if (_result is RuntimeResult result)
{
await message.Channel.SendMessageAsync(result.Reason);
}
else if (!_result.IsSuccess)
{
// Previous error handling
}
```
The RuntimeResult class can be subclassed too, for example:
```csharp
var _result = await Commands.ExecuteAsync(context, argPos);
if (_result is MySubclassedResult result)
{
var builder = new EmbedBuilder();
for (var pair in result.Data)
{
builder.AddField(pair.Key, pair.Value, true);
}
await message.Channel.SendMessageAsync("", embed: builder);
}
else if (_result is RuntimeResult result)
{
await message.Channel.SendMessageAsync(result.Reason);
}
else if (!_result.IsSuccess)
{
// Previous error handling
}
```
* Make RuntimeResult's ctor protected
* Make RuntimeResult abstract
It never really made sense to have it instantiable in the first place,
frankly.
* Add grouping of preconditions to allow for flexible precondition logic.
* Fix checking Module Preconditions twice (and none of the command's own)
* Fix command preconditions group 0 looping over every other precondition anyway #whoopsies
* Use custom message when a non-zero Precondition Group fails.
* Fix doc comment rendering.
* Refactor loops into local function
* Considering a new result type
* Switch to IReadOnlyCollection<T> and fix compiler errors
* Revert PreconditionResult -> IResult in return types - Change PreconditionResult to a class that PreconditionGroupResult inherits.
* Feedback on property name.
* Change grouping type int -> string
* Explicitly use an ordinal StringComparer
* Full stops on error messages
* Remove some sillyness.
* Remove unneeded using.
