Add SVG watermark image to log view and some tabs.

main.css

@@ -39,21 +39,33 @@ input[type="number"]::-webkit-inner-spin-button {
     height: calc(100% - 5px);
 }
 
+#content-watermark {
+    position: absolute;
+    bottom: 40px;
+    left: 0;
+    right: 0;
+    z-index: 1;
+    overflow: hidden;
+    background-image: url("images/light-wide-1.svg");
+    background-repeat: no-repeat;
+    background-position: 50% 0%;
+    background-size: 600px;
+    height: 174px;
+    opacity: 0.25;
+}
+
 #watermark {
     position: absolute;
-    text-align: center;
-    top: 35px;
-    left: 0;
-    bottom: 0;
+    top: 30px;
+    height: 67px;
     right: 0;
     z-index: -1;
     overflow: hidden;
-
-    font-family: monospace;
-    color: grey;
-    font-size: 50px;
-    font-variant: small-caps;
-    letter-spacing: 0.5em;
+    background-image: url("images/light-wide-1.svg");
+    background-repeat: no-repeat;
+    width: 340px;
+    background-position: 0px 0px;
+    background-size: 85%;
 }
 
 #port-picker {

main.html

@@ -126,7 +126,7 @@
             </div>
             <div class="clear-both"></div>
             <div id="log">
-                <div id="watermark">CleanFlight</div>
+                <div id="watermark"></div>
                 <div class="wrapper">
                 </div>
             </div>

tabs/cli.html

@@ -1,3 +1,4 @@
+<div id="content-watermark"></div>
 <div class="tab-cli">
     <p i18n="cliInfo">
     </p>

tabs/dataflash.html

@@ -1,3 +1,4 @@
+<div id="content-watermark"></div>
 <div class="tab-dataflash">
     <div class="require-dataflash">
         <div class="note" i18n="dataflashNote">

tabs/logging.html

@@ -1,3 +1,4 @@
+<div id="content-watermark"></div>
 <div class="tab-logging">
     <div class="note" i18n="loggingNote">
     </div>

tabs/motors.html

@@ -1,3 +1,4 @@
+<div id="content-watermark"></div>
 <div class="tab-motors">
     <div class="wrapper modelAndAccel">
         <div class="mixerPreview">

tabs/pid_tuning.html

@@ -1,3 +1,4 @@
+<div id="content-watermark"></div>
 <div class="tab-pid_tuning">
     <div class="controller">
         <span class="head" i18n="pidTuningControllerHead"></span>

tabs/ports.html

@@ -1,3 +1,4 @@
+<div id="content-watermark"></div>
 <div class="tab-ports">
     <div class="help">
         <p i18n="portsHelp"></p>

tabs/receiver.html

@@ -1,3 +1,4 @@
+<div id="content-watermark"></div>
 <div class="tab-receiver">
     <div class="bars">
     </div>

tabs/sensors.html

@@ -1,3 +1,4 @@
+<div id="content-watermark"></div>
 <div class="tab-sensors">
     <div class="info">
         <p i18n="sensorsInfo">