Better audio management (#10)

* add audio_session package

* `AudioManager` initial design

* try to integrate audio manager

* configure audio session

* `DisposeAware`

disposing if already published causes exception.

* organize

* guard flutter_webrtc calls

* websocket async fix

* use `ConnectionState` instead of `_isClosed` and `isReconnecting`

* change create audio track defaults

* update protos

* protocol 3 speaker updates

* fix exception

* emit `RoomDisconnectedEvent` only once

* fix exception

* keep track of local / remote audio tracks

* explicit types

* manage track state

* re-structure audio management

* change defaults

* unpublish all

* use experimental build

* change defaults

* configuring is optional

* call native `RTCAudioSession.setConfiguration`

* defaults adjustment

* iOS only for now

* use lib 92.4515.07

* clean up

* revert audio options for now

* remove pod source

* rename apple related audio

* `createListener` method

* organize native audio

* `SpeakingChangedEvent` only on `Participant`

* refactoring

* fix ios compile

* fix configure audio only for iOS logic

* minor fix & clean up

* change dispose logic

* format protos

* fix unpublishTrack

* `createListener` into a mixin

* simplify

* use flutter_webrtc master

* unpublish for example

* update ios icon

* android icon

* web icon

* favicon

example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "1020"
+   LastUpgradeVersion = "1300"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -27,8 +27,6 @@
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       shouldUseLaunchSchemeArgsEnv = "YES">
-      <Testables>
-      </Testables>
       <MacroExpansion>
          <BuildableReference
             BuildableIdentifier = "primary"
@@ -38,8 +36,8 @@
             ReferencedContainer = "container:Runner.xcodeproj">
          </BuildableReference>
       </MacroExpansion>
-      <AdditionalOptions>
-      </AdditionalOptions>
+      <Testables>
+      </Testables>
    </TestAction>
    <LaunchAction
       buildConfiguration = "Debug"
@@ -61,8 +59,6 @@
             ReferencedContainer = "container:Runner.xcodeproj">
          </BuildableReference>
       </BuildableProductRunnable>
-      <AdditionalOptions>
-      </AdditionalOptions>
    </LaunchAction>
    <ProfileAction
       buildConfiguration = "Profile"