[ENHANCEMENT] Add a lattice q-vector generator that does not depend on the width option

**Is your feature request related to a problem? Please describe.**
The current lattice q-vector generator does not allow width=0. Setting a small width with the current lattice q-vector generators means that I might get zero valid q-vectors for a specific value of |q|,

**Describe the solution you'd like**
Add a new lattice q-vector generator which generates all valid lattice q-vectors within a specific range. Unlike the current lattice q-vector generators, the q-vector step won't be constant. We might need an option to set the maximum number of q-vectors used for a given shell. Adding a preview of the q-vector shells that will be created with this generator in the GUI might also be useful.