Update spahm-b

[YAY-C]

• [x] add same-basis option
• [x] implement single atom-type rep. generation and param
• [x] ecp argument for CLI parser
• [x] Add test
• [x] what about the --symbol option vs spahm-a(keep or remove)

(Closes #47)

[briling]

• [x] add the docs please!

[briling]

• [x] please add same_basis to bond_selected or whatever