New +themes with more colors

[mxub]

Like I mentioned in #102 I created plus versions for your themes that have some new behavior:

1. main color indicates active tabs
2. there are secondary and tertiary colors for active & modified and inactive & modified

Here some screenshots to show what I mean:

(assets.json is changed but not saved)

blue+

a    : blue
a + m: purple
i + m: magenta

green+

a    : green
a + m: orange
i + m: magenta

magenta+

a    : magenta
a + m: orange
i + m: blue

orange+

a    : orange
a + m: blue
i + m: magenta

[mxub]

see #104