Add additional video player keyboard shortcuts (#275)

*  Skip forward 10 seconds ((CMD OR CTRL) ALT right)
 Skip back 10 seconds ((CMD OR CTRL) ALT left)
 Increase video speed ((CMD OR CTRL) +)
 Decrease video speed ((CMD OR CTRL) -)

* Codestyle fix

* The 'steps' should be implemented in base2, standard players use 1x, 2x, 4x, 8x, 16x

fixed bug with shift + "=" which is "+"

* resolve conflicts

* remove ide specific data
make playback rate more granular
add to menu skip and speed entries

* intendation fix

* conflict resolve

* rename setPlaybackRate to changePlaybackRate
setRate return boolean depending on whether this cast target supports setting the playback rate.
if setRate returns false - don`t change state
redundant else if statement in changePlaybackRate function

renderer/lib/cast.js

@@ -8,7 +8,8 @@ module.exports = {
   play,
   pause,
   seek,
-  setVolume
+  setVolume,
+  setRate
 }
 
 var airplay = require('airplay-js')
@@ -344,6 +345,22 @@ function pause () {
   }
 }
 
+function setRate (rate) {
+  var device
+  var result = true
+  if (state.playing.location === 'chromecast') {
+    // TODO find how to control playback rate on chromecast
+    castCallback()
+    result = false
+  } else if (state.playing.location === 'airplay') {
+    device = state.devices.airplay
+    device.rate(rate, castCallback)
+  } else {
+    result = false
+  }
+  return result
+}
+
 function seek (time) {
   var device = getDevice()
   if (device) {