Fix duplicated lodash package when bundling react-admin without tree shaking

[impronunciable]

Importing lodash instead of lodash/merge was having an impact in the ra-core import size for examples/demo.

This is lodash footprint before the change:

And after:

[fzaninotto]

The import you changed is only one of many. You're supposed to use a bundler with tree-shaking ability to minimize your bundle size.

[impronunciable]

Actually it was the only one importing the main lodash module. That's why I got the file size reduction. I think this would be beneficial for every ra user even if they don't use a bundler with tree shaking

[fzaninotto]

You're right, all the other imports use the alternative syntax. So not only does your PR improve bundle size for those not using a bundler with tree shaking, it also makes the code more consistent. Let me reopen and merge it.

[fzaninotto]

Thanks for this patch. Note that using a bundler with tree shaking will reduce the bundle size even more (because we use mostly the import { XXX } from ... syntax for material-ui).

[impronunciable]

Thank you and thanks for mantaining the project!