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/max31855/CMakeLists.txt

@@ -1,5 +1,5 @@
 set (libname "max31855")
-set (libdescription "K type thermistor amplifier")
+set (libdescription "Thermocouple-to-Digital Converter")
 set (module_src ${libname}.cxx)
 set (module_hpp ${libname}.hpp)
 upm_module_init(mraa)

src/max31855/max31855.hpp

@@ -37,10 +37,11 @@ namespace upm {
 /**
  * @library max31855
  * @sensor max31855
- * @comname MAX31855 Thermocouple Amplifier
+ * @comname Thermocouple-to-Digital Converter
  * @type other
  * @man maxim adafruit
  * @con spi
+ * @web https://www.maximintegrated.com/en/products/analog/sensors-and-sensor-interface/MAX31855.html
  *
  * @brief API for the MAX31855 Thermocouple Amplifier
  *