…tream, canal & river lines

Change river color to #8fcadd - Lch(78,21,227)
The color of river, canal, ditch and drain lines is changed to `@river-color` in `#8fcadd` to be more visible over forest and other dark landcover areas.
The color of river and canal areas is changed to match. This also improves mapper feedback about tagging of water areas
Added a new intermittent_river.png pattern in the new river-color

    Adds @ocean-color: #b9d3dc - Lch(83,10,227), 5 lower chroma and 1 higher lightness than water-color

@water-color: #a2d1e0;     // Lch(81,17,227)
@ocean-color: #b5d7e3;     // Lch(84,13,227)
@river-color: #8fcadd;     // Lch(78,21,227)

This is not a perfect solution and depends on river color being
the darkest but it seems to work all right even on ocean.