Add extended advertising support. (#72)

Adds support for advertising and connections with coded/2M PHY's.

Adds new classes `NimBLEExtAdvertising` and `NimBLEExtAdvertisement`.
When extended advertising is enabled the original advertising classes become unavailable and the new classes must be used.

Changed some return values for advertising methods for consistency with the new classes methods.

examples/Bluetooth_5/NimBLE_extended_server/main/component.mk

@@ -0,0 +1,4 @@
+#
+# "main" pseudo-component makefile.
+#
+# (Uses default behaviour of compiling all source files in directory, adding 'include' to include path.)