This adds and implements `open func modifyValue(_ v: Any?, forKey k: String) -> Any` to the `StORM` class.
The intent of this addition is to allow base classes to optionally change the data sent to the database. For example, I am using it to properly handle `Optional`s and the `Date` class in PostgreSQL as follows:
```swift
override func modifyValue(_ val: Any, forKey k: String) -> Any {
var v = val
if let o = val as? OptionalProtocol {
if o.isSome() {
v = o.unwrap() // not-nil
} else {
return "" // nil
}
}
// After this point, v is guarenteed to not be optional or nil
if let d = v as? Date {
return d.timestamptz
}
return v
}
```
The implementations of `OptionalProtocol` and `timestamptz` are irrelevant for this pr.
The `forKey` parameter is there in case someone wants to switch based on name, not on value.
The name is just a placeholder, so feel free to change it if you think of something better.
thislooksfun