compiler, runtime, common, documentation: Refactor Type System

The type system (and the value system) now include attributes
for each type (things like direction, const-ness).

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Snippets/use-program-instanceswithtypes.swift

@@ -39,8 +39,8 @@ let p4_program_with_control_decl = """
 
 
 // snippet.include
-let flter = { (tipe: P4TypeAttributed) -> Bool in
-  switch tipe.type {
+let flter = { (tipe: P4Type) -> Bool in
+  switch tipe.dataType(){
   case let c as Control: c.name == "simple"
   default: false
   }

Snippets/use-program-typeswithtypes.swift

@@ -32,7 +32,7 @@ let p4_program_with_struct_decl = """
   """
 
 // snippet.include
-let flter = { (tipe: P4Type) -> Bool in
+let flter = { (tipe: P4DataType) -> Bool in
   switch tipe {
   case let c as P4Struct: c.name == "agg"
   default: false