* `allSymbols` -> `toSeq`
* added `fromSeq :: Seq (Identifier, Symbol) -> SymbolTable`
* `type SymbolTable = Map.Map Identifier (Map.Map Scope Symbol)`
* added `member :: Identifier -> Stack Scope -> SymbolTable -> Bool`
* Made Definition.hs and TypeChecker.hs compatible with said changes
Styling
Put Printer.hs into Program.hs, now is `PrettyShow`