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/l3gd20/CMakeLists.txt

@@ -1,5 +1,5 @@
 set (libname "l3gd20")
-set (libdescription "L3gd20 sensor module")
+set (libdescription "Tri-axis Digital Gyroscope")
 set (module_src ${libname}.cxx)
 set (module_hpp ${libname}.hpp)
 upm_module_init(mraa)

src/l3gd20/l3gd20.hpp

@@ -49,10 +49,11 @@ namespace upm
 /**
  * @library l3gd20
  * @sensor l3gd20
- * @comname L3GD20 Tri-axis Digital Gyroscope
+ * @comname Tri-axis Digital Gyroscope
  * @type gyroscope
  * @man stmicro
  * @con iio i2c
+ * @web http://www.st.com/en/mems-and-sensors/l3gd20.html
  *
  * @brief L3GD20 Tri-axis Digital Gyroscope API
  *