use fetch and update js and add some buttons for webpage

data/index.html

@@ -1,6 +1,7 @@
 <!DOCTYPE html>
 <html>
-  <meta name="viewport" content="width=device-width, initial-scale=1.0">
+<meta name="viewport" content="width=device-width, initial-scale=1.0">
+
 <head>
   <title>ESP8266 Treppenlicht</title>
   <link href="/favicon.png" rel="icon" type="image/png" sizes="10x10">
@@ -10,6 +11,12 @@
 <body>
   <div class="topbar">Treppenlicht</div>
 
+  <div class="param_block">
+    <input type="button" class="control" data-action="s_oben" value="sensor_oben">
+    <input type="button" class="control" data-action="s_unten" value="sensor_unten">
+    <input type="button" class="control" data-action="on_off" value="on_off">
+  </div>
+
   <div class="param_block">
     Active Brightness: <output id="out_act_pwm" class="val_range">50</output> %
     <div class="slider">
@@ -17,7 +24,6 @@
     </div>
   </div>
 
-
   <div class="param_block">
     Idle Brightness Maximum: <output id="out_idl_pwm" class="val_range">50</output> %
     <label id="note">[100% == Active Brightness]</label>
@@ -51,7 +57,7 @@
 
 
   <div class="terminal">
-    <input type="button" id="clear_term" value="clear" onclick="clearTerminal();">
+    <input type="button" id="clear_term" value="clear">
     <input type="checkbox" id="scroll" name="scroll" value="scroll" checked>
     <label for="scroll"> autoscroll </label>
     <textarea id="term">waiting for log messages ...&#10;</textarea>