W1 option take-over into W2

[Juergen Reuter]

1. keep best grid as fall back option like W1
   1. allow to ignore checksum test
   2. gzipped grid files (via named pipes) and process subdirectories
   3. safety_factor, flag events w/weight > 1 (plot_excess)
   4. events_per_file, including starting number
   5. signal handling: save/restore vamp grid CONTENTS
   6. show_* for debug output format

obsolete:

1. use_efficiency (efficiency fluctuates)
2. time_limit_adaptation (dangerous and machine dependent)
3. generate_phase_space (old development flag)
4. write_phase_space_channels_file
5. extra_off_shell_lines
6. splitting_depth (only single logs, not important)
7. single/double_off_shell_branchings/decays
8. massive_fsr
9. single/double_off_shell_branchings/decays
10. massive_fsr
11. write_weights/write_weights_file
12. guess_color_flow
13. pythia_processes
14. time_limit (only for hard nosed batch systems)
15. warn_empty_channel (only for pathological cases)
16. show_pythia_initialization
17. show_pythia_statistics
18. screen_events, screen_histograms
19. screen_diagnostics
20. plot_grids_channels, plot_grids_logscale (impractical for large number of channels?)

implemented:

1. fragment/fragmentation_method
2. plot_width, plot_height
3. accuracy_goal

[kilian]

OK, let's start working on this ...

[kilian]

accuracy_goal: done in r3658.

There are now three goals: accuracy_goal, error_goal, relative_error_goal. If all goals that are set have been reached in the adaptation pass, the rest of the adaptation pass is skipped and WHIZARD proceeds with the final integration pass.

The nontrivial part was to make this work correctly with iterations read from file. They are reused where possible, even if the goals are changed in a second run.