Blueprint - option for visible menu depth

[Marco Krapf]

• add option in blueprint for menu depth:

maxdepth: number (kirby optional, default show depth 3)

e.g

• if you set maxdepth to 1, just level one is visible even if there are sublevel
• if you set maxdepth to 3, all levels up to 3 are shown.

e.g

• menu1
• menu2

• menu3

  • sub1
  • sub2

  • sub3

    • sub1
    • sub2

  • sub4

• menu4