Theme support for CRUD screens

[ankit-agrawal11]

Originally reported by: Nahush Farkande (Bitbucket: nahushfcc, GitHub: Unknown)

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In the cli, Add support for a theme flag which will generate the file inside <themeName>/components/<resource> instead of simply components/<resource>.

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• Bitbucket: https://bitbucket.org/causecode/react-hero/issue/4