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/app.js

@@ -26,7 +26,8 @@ function App (state) {
     state.playing.mouseStationarySince !== 0 &&
     new Date().getTime() - state.playing.mouseStationarySince > 2000 &&
     !state.playing.isPaused &&
-    state.playing.location === 'local'
+    state.playing.location === 'local' &&
+    state.playing.playbackRate === 1
 
   // Hide the header on Windows/Linux when in the player
   // On OSX, the header appears as part of the title bar