Fix eslint warning

[longshuicy]

There are 24 warnings so far; will tighten the loose ends eventually.

/Users/cwang138/Documents/Clowder/clowder-frontend-prototype/src/components/Dashbard.tsx
12:33 warning 'RootState' is defined but never used no-unused-vars
12:44 warning 'Thumbnail' is defined but never used no-unused-vars
181:13 warning Missing "key" prop for element in iterator react/jsx-key

/Users/cwang138/Documents/Clowder/clowder-frontend-prototype/src/components/Dataset.tsx
27:9 warning 'FileMetadataList' is defined but never used no-unused-vars
27:27 warning 'RootState' is defined but never used no-unused-vars
27:38 warning 'Thumbnail' is defined but never used no-unused-vars
266:13 warning Missing "key" prop for element in iterator react/jsx-key

/Users/cwang138/Documents/Clowder/clowder-frontend-prototype/src/components/File.tsx
11:9 warning 'PreviewConfiguration' is defined but never used no-unused-vars
11:31 warning 'RootState' is defined but never used no-unused-vars
157:20 warning Missing "key" prop for element in iterator react/jsx-key

/Users/cwang138/Documents/Clowder/clowder-frontend-prototype/src/components/childComponents/UploadFile.tsx
39:4 warning Unexpected console statement no-console

/Users/cwang138/Documents/Clowder/clowder-frontend-prototype/src/reducers/dataset.ts
3:9 warning 'DataAction' is defined but never used no-unused-vars
4:9 warning 'DatasetState' is defined but never used no-unused-vars

/Users/cwang138/Documents/Clowder/clowder-frontend-prototype/src/reducers/file.ts
7:9 warning 'DataAction' is defined but never used no-unused-vars
8:9 warning 'FileState' is defined but never used no-unused-vars

/Users/cwang138/Documents/Clowder/clowder-frontend-prototype/src/types/global.d.ts
1:15 warning 'ENV' is defined but never used no-unused-vars
2:15 warning 'PUBLIC_PATH' is defined but never used no-unused-vars
40:14 warning 'React' is defined but never used no-unused-vars

/Users/cwang138/Documents/Clowder/clowder-frontend-prototype/src/utils/common.js
2:8 warning 'jwt_decode' is defined but never used no-unused-vars

/Users/cwang138/Documents/Clowder/clowder-frontend-prototype/src/utils/dataset.js
59:3 warning Unexpected console statement no-console
62:3 warning Unexpected console statement no-console

/Users/cwang138/Documents/Clowder/clowder-frontend-prototype/src/utils/file.js
75:3 warning Unexpected console statement no-console
78:3 warning Unexpected console statement no-console

/Users/cwang138/Documents/Clowder/clowder-frontend-prototype/src/utils/thumbnail.js
5:54 warning 'title' is assigned a value but never used no-unused-vars

✖ 24 problems (0 errors, 24 warnings)