auto add k-label

[373Kice]

1. Auto add k-label from KPOINTS file. The K-label in KPOINTS file must be split by "!", such as "0.0 0.0 0.0 ! \Gamma".
2. You can select part of the band to plot by "--section". Using : pyband --section 1 -- section 2
3. Plot mbj-type band, need IBZKPT file and KPOINTS.band. Just plot the point with a weight of 0 at the KPOINTS file. Using "pyband --fkpoints=KPOINTS.band" to add k-label from KPOINTS.band
4. Change the font to 'Times New Roman' .... for myself. :)