Make main functions callable from command line

Make main functions callable from command line. Already done it for `conf_grid` where the three options to call it are:
- `conf_grid`: opens GUI
- `conf_grid(grid)`: calls the structure `grid` that contains all the input parameters and bypasses the GUI functions
- `grid = conf_grid`: returns an empty template structure

### Input
- [x] `conf_grid`
- [ ] `dwind`