[#488] reputation: Change Writer interface

Includes:
- Delete first `ctx` argument in `Write` method.
- Move intermediate Initial trust struct and method
to `calculator` file.
- Change Alpha to 0.1.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

pkg/services/reputation/local/storage/storage.go

@@ -9,7 +9,7 @@ import (
 // All values must comply with the requirements imposed on them.
 // Passing incorrect parameter values will result in constructor
 // failure (error or panic depending on the implementation).
-type Prm struct {}
+type Prm struct{}
 
 // Storage represents in-memory storage of
 // local reputation values.