Store min and max values of all quantities in sww file

[ole]

A viewer that colour-codes surfaces based on values of quantities will need the range of each quantities. Otherwise the viewer would have to read the entire sww file everytime it is launched.

To alleviate that, I propose that we introduce an array of lenght 2 for each quantity in the sww file which will store the minimal vertex value and the maximal vertex value encountered for all triangles and all timesteps. These should be updated every time a new timestep is stored into the sww file.

Example

stage_range = [3.1, 10.7]

means that vertex values in stage have never been smaller than 3.1 or larger than 10.7 anywhere or anytime so far.

The arrays could be named:

stage_range xmomentum_range ymomentum_range elevation_range (just in case) friction_range

[Duncan <duncan@…>]

We don't need elevation_range and friction_range.

[ole]

Please put a pointer to the changeset that implemented this ticket.

[duncan]

This was implemented by changeset:4455.