Revise paper-output limitation on color gamut

**Description of the desired feature**

Way back when plotting color on paper was very important, we (via @WalterHFSmith) limited the range of HSV saturation and value parameters since for values close to 0 no printer could distinguish between blackish red and reddish black... However, when graphics is simply made for viewing digitally then these limitations no longer make sense since monitors are better able to show the full gamut of colors. The parameters in question and their defaults are

```
COLOR_HSV_MAX_S = 0.1
COLOR_HSV_MIN_V = 0.3
```

In making animations with **gmt movie** there is guaranteed to be no paper to worry about, and I have learned the hard way (more than once, in fact) I need to override these settings with

```
COLOR_HSV_MAX_S = 0
COLOR_HSV_MIN_V = 0
```

to allow for continuous color variations across the full gamut, including in stuff like fading in and out from black. This brings up two possible solutions:

1. I already started to make a _movie_ theme file which sets those parameters; it may change other settings too that may make less sense outside animations, such as setting **MAP_ORIGIN_X** = **MAP_ORIGIN_Y** = 0 to simplify composition. However, we took it out of the gmt-theme branch for now. Plus, users would _still_ need to know why they should switch to theme.
2. We let the **movie** module quietly override those 0.1/0.3 defaults.

I think we face an uphill battle to educate users on the technical points here but we definitively want to prevent users trying to make movies using color defaults suitable for paper. So, perhaps option 2 is the best one here? Then again, perhaps printer technology has advanced since 1990 and we should simply change those defaults to 0,0 permanently and instead let these settings be available for experts who know what they are doing and have specific ranges of HSV in mind.

Thoughts, @GenericMappingTools/core ?