[Breaking] Change all time input parameters to milliseconds. (#78)

Changes all functions that accept a time parameter to use milliseconds instead of seconds.

* Adds duration input to NimBLEDevice::startAdvertising and NimBLEServer::startAdvertising.

src/NimBLEServer.h

@@ -59,7 +59,7 @@ public:
     bool                   stopAdvertising(uint8_t inst_id);
 #else
     NimBLEAdvertising*     getAdvertising();
-    bool                   startAdvertising();
+    bool                   startAdvertising(uint32_t duration = 0);
 #endif
     bool                   stopAdvertising();
     void                   start();