camera_def: add parameter ranges (#553)

* camera_def: add parameter ranges

This is just reflecting what's implemented in QGC and MAVSDK.

Also see:
- https://github.com/mavlink/MAVSDK/blob/v2.12/src/mavsdk/plugins/camera/camera_definition.cpp#L368-L413
- https://github.com/mavlink/qgroundcontrol/blob/be1e2d46c95812d3ad700bdc4807eca95829be6b/src/Camera/VehicleCameraControl.cc#L968-L1014

* Apply suggestions from code review

* Show equivalence and state restrictions

---------

Co-authored-by: Hamish Willee <hamishwillee@gmail.com>

Author: julianoes

en/services/camera_def.md

@@ -195,7 +195,7 @@ There are cases where an option change requires a parameter to be updated. For e
 
 This tells the GCS that when the `CAM_EXPMODE` parameter changes, the `CAM_APERTURE`, `CAM_SHUTTERSPD` and the `CAM_ISO` parameters must be updated (requested from the camera).
 
-#### Range Limit
+#### Option Range Limit
 
 Suppose your camera has the following ISO options:
 
@@ -248,6 +248,34 @@ This indicates to the GCS that when the `CAM_MODE` parameter is set to _Video_,
 
 This example also tells the GCS not to display this parameter to the user (`control=“0”`). Camera Mode is a standard parameter defined in the [CAMERA_INFORMATION](../messages/common.md#CAMERA_INFORMATION) message and it’s handled by the GCS in that way. The parameter definition above was created in order to tell the GCS the rules that are applied when changes to the camera mode occur.
 
+#### Param Ranges
+
+It is also possible to define param ranges without individual options, but by specifiying the minimum, maximum, and optionally a step size:
+
+```xml
+<parameter name="CAM_APERTURE" type="float" default="2.8" min="2.8" max="14.0" step="0.1">
+    <description>Aperture</description>
+</parameter>
+```
+
+This would be equivalent to:
+
+```xml
+<parameter name="CAM_APERTURE" type="float" default="2.8">
+    <description>Aperture</description>
+    <options>
+      <roption name="2.8" value="2.8" />
+      <roption name="2.9" value="2.9" />
+      ...
+      <roption name="13.9" value="13.9" />
+      <roption name="14" value="14" />
+    </options>
+</parameter>
+```
+
+Note that this approach cannot be used in conjunction with exclusions or option range limits (defined with `parameterrange`).
+Therefore it is recommended for cases where the range of allowed values does not vary with any other camera mode or setting.
+
 ### Localization
 
 The `localization` element is used for defining localized strings for display to users. If found, the GCS will use to replace all `description` and options `name` values found in the file with the strings defined here. Here is an example for German localization (de_DE):