Global namespace declaration support

[dsherret]

Better support for namespace declarations that use the syntax global {}.

Deprecating:

• .setHasNamespaceKeyword
• .setHasModuleKeyword
• NamespaceDeclarationStructure - hasModuleKeyword and hasNamespaceKeyword

Adding:

• enum NamespaceDeclarationKind { Namespace = "namespace", Module = "module", Global = "global" }
• setDeclarationKind(kind: NamespaceDeclarationKind)
• getDeclarationKind(): NamespaceDeclarationKind;
• NamespaceDeclarationStructure - declarationKind: NamespaceDeclarationKind

[coveralls]

Coverage decreased (-0.2%) to 95.046% when pulling cd0e511 on globalNamespaceSupport into 1ca6dd3 on dev.