A couple of fixups prior to merging into main project

Changed the ds_sensor_t struct to just return a float instead of major/minor
Renamed ds18b20.h functions to have consistent `ds18b20_*` naming.
Removed some unnecessary LICENSE files.  Clarified onewire origin/license.

extras/onewire/LICENSE

@@ -20,3 +20,12 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 
+-------------------------------------------------------------------------------
+
+Portions copyright (C) 2000 Dallas Semiconductor Corporation, under the
+following additional terms:
+
+Except as contained in this notice, the name of Dallas Semiconductor
+shall not be used except as stated in the Dallas Semiconductor
+Branding Policy.
+

extras/onewire/README.md

@@ -1,7 +1,14 @@
 # Yet another one wire driver for the ESP8266
 
-This is a port of bit banging one wire driver based on nodemcu implementaion.
+This is a port of a bit-banging one wire driver based on the implementation
+from NodeMCU.
 
-Seams that they port it from  https://www.pjrc.com/teensy/td_libs_OneWire.html
+This, in turn, appears to have been based on the PJRC Teensy driver
+(https://www.pjrc.com/teensy/td_libs_OneWire.html), by Jim Studt, Paul
+Stoffregen, and a host of others.
 
-For all aspect regarding license, please check LICENSE file and coresponding projects.
+The original code is licensed under the MIT license.  The CRC code was taken
+(at least partially) from Dallas Semiconductor sample code, which was licensed
+under an MIT license with an additional clause (prohibiting inappropriate use
+of the Dallas Semiconductor name).  See the accompanying LICENSE file for
+details.