add plots after run_model

[ronaldtanner]

Following plots should be createable on demand (See script.profemag.ch:)

• Field Lines
• Color gradation: Babs, Bx, By, Br, Bt, Habs, Hx, Hy, Hr, Ht, relperm, rem, Wm, Bdev, Mrdev, Vpot, demoag, pmfelosd

either with automatic or explicit scaling.

Examples:

• plots=['field_lines', 'Babs']
• plots=[('field_lines', 10) , ('Babs', 0, 2.0)]