feat(jsii-spec): Model parameter optionality

Method `Parameters` now carry an `optional` flag that indicates whether
they are optional or required, and the `TypeReference#optional` field
was renamed to `TypeReference#nullable` to better reflect its semantics.

This also brings more flexibility in that it is now possible to model a
method with a nullable or defaulted argument that is followed by some
non-optional argument, and still obtain a reasonable type specification,
where previously this was an error.

Finally, in order to better reflect the type model of TypeScript and
Javascript, all `any` type references are now denoted `nullable`.

BREAKING CHANGE: JSII assemblies generated by older versions of the tool
will fail loading with this new version, and vice-versa. Re-compile your
projects in order to fix this.

Fixes #296
Fixes #414

package.json

@@ -5,7 +5,7 @@
 		"lerna": "^3.13.1",
 		"nodeunit": "^0.11.3",
 		"nyc": "^13.3.0",
-		"tslint": "^5.13.0",
-		"typescript": "^3.3.3333"
+		"tslint": "^5.15.0",
+		"typescript": "^3.4.1"
 	}
 }

packages/codemaker/package.json

@@ -16,7 +16,7 @@
     "@types/node": "^8.10.43",
     "@types/nodeunit": "^0.0.30",
     "nodeunit": "^0.11.3",
-    "typescript": "^3.3.3333"
+    "typescript": "^3.4.1"
   },
   "dependencies": {
     "camelcase": "^5.2.0",

packages/jsii-calc-base/test/assembly.jsii

@@ -82,6 +82,7 @@
           },
           "name": "typeName",
           "returns": {
+            "nullable": true,
             "primitive": "any"
           }
         }
@@ -112,5 +113,5 @@
     }
   },
   "version": "0.8.2",
-  "fingerprint": "lIcHicx5rBBxyy5vOvOqvbBGjk//8lFLX6oVx2xh5Fc="
+  "fingerprint": "f/Vo5ezvqYp8jwokKJftL6t8IIXU2GGM17L/jKRF2oQ="
 }

packages/jsii-calc-lib/test/assembly.jsii

@@ -191,7 +191,7 @@
               },
               "kind": "array"
             },
-            "optional": true
+            "nullable": true
           }
         }
       ]
@@ -307,7 +307,7 @@
           "immutable": true,
           "name": "optional1",
           "type": {
-            "optional": true,
+            "nullable": true,
             "primitive": "string"
           }
         },
@@ -316,7 +316,7 @@
           "immutable": true,
           "name": "optional2",
           "type": {
-            "optional": true,
+            "nullable": true,
             "primitive": "number"
           }
         },
@@ -325,7 +325,7 @@
           "immutable": true,
           "name": "optional3",
           "type": {
-            "optional": true,
+            "nullable": true,
             "primitive": "boolean"
           }
         }
@@ -373,5 +373,5 @@
     }
   },
   "version": "0.8.2",
-  "fingerprint": "SDQQzBvYRO3SXfWWgpKwLDSy3EgMqP/e6rd75kblKA0="
+  "fingerprint": "Y9xi2LtDOP8ebtxdHcYvi9Bo9Gj/JbjNJ5GP22d3dJk="
 }