doc: Scrubbed ALL sensor library descriptions

In an effort to clean-up and standardize UPM library
documentation, this commit updates (and in most cases,
unifies) the CMake description string AND CXX header
@comname string.

Strings were taken from datasheets when possible, spelling
mistakes were addressed, copy/paste errors where fixed,
Title Case was used, etc.

    * Tested/updated/added @web tags
    * Added/updated invalid sensor images
    * Added/updated @man tags, added missing manufacturers

Signed-off-by: Noel Eck <noel.eck@intel.com>

src/mg811/CMakeLists.txt

@@ -1,5 +1,5 @@
 set (libname "mg811")
-set (libdescription "DFRobot CO2 sensor")
+set (libdescription "CO2 Sensor")
 set (module_src ${libname}.cxx)
 set (module_hpp ${libname}.hpp)
 upm_module_init(mraa)

src/mg811/mg811.hpp

@@ -38,7 +38,7 @@ namespace upm {
   /**
    * @library mg811
    * @sensor mg811
-   * @comname DFRobot CO2 Sensor
+   * @comname CO2 Sensor
    * @altname MG811
    * @type gaseous
    * @man dfrobot