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/views/player.js

@@ -48,6 +48,9 @@ function renderMedia (state) {
       mediaElement.currentTime = state.playing.jumpToTime
       state.playing.jumpToTime = null
     }
+    if (state.playing.playbackRate !== mediaElement.playbackRate) {
+      mediaElement.playbackRate = state.playing.playbackRate
+    }
     // Set volume
     if (state.playing.setVolume !== null && isFinite(state.playing.setVolume)) {
       mediaElement.volume = state.playing.setVolume
@@ -440,6 +443,12 @@ function renderPlayerControls (state) {
     </span>
   `)
 
+  // render playback rate
+  if (state.playing.playbackRate !== 1) {
+    elements.push(hx`
+     <span class="rate">speed: ${state.playing.playbackRate}X</span>
+    `)
+  }
   // Finally, the big button in the center plays or pauses the video
   elements.push(hx`
     <i class='icon play-pause' onclick=${dispatcher('playPause')}>