Refactor `MetataProperty` to support dynamic properties

[samchon]

To support dynamic properties (#153), type of MetadataProperty.name must be changed from string to Metadata.

However, MetadataProperty already has been possessed the Metadata type in the MetadataProperty.metadata property. For clean design, it would better to rename MetadataProperty.name to key and MetadataProperty.metadata as value. Therefore, after implementing following this issue, MetadataProperty would be like below:

export class MetadataProperty {
    public readonly key: Metadata;
    public readonly value: Metadata;
    public readonly description: string | undefined;
    public readonly tags: IMetadataTag[];
    public readonly jsDocTags: IJsDocTagInfo[];
}

Also, many Programmer classes would be refactored by this change.