Different Frontname for Grid Component

[astorm]

From: https://github.com/astorm/pestle/pull/267

The names for the layout files generated for each controller action assume that the frontname for the route will be the namespace_modulename. Perhaps a prompt can be added for the frontname and that can be used to choose the file name.

Do we want this as a prompt, or an option? (the tradeoff being another prompt adds a bit of additional complexity for first time users, but an option hides advanced functionality for power users).