* LinearButtonGroupManager class now have the same functionality as
  ButtonGroupManager class had before.
* ButtonGroupManager now is the base class for all other button group
  managers.
* Appropriate fixes in the CAR plugin.

* Implemented LinearSmoothedValueAtomic class based on the
  JUCE 4.0 library' LinearSmoothedValue class but with some improvements
  that were suggested by Timur Doumler during his JUCE Summit 2015
  talk.
* LinearSmoothedValueAtomic is very convenient to use with float values
  that need linearly smoothed behaviour (like volume, etc.) and which
  are shared between several threads (i.e. audio and GUI).
* This class guarantees we won't have any race conditions and it will
  remains lock-free because of using std::atomic inside it.

* Implemented ButtonGroupManager.
  It is responsible for positioning of buttons, any animations
  during switching, etc.
* Added MaterialButtonLookAndFeel class which implements
  flat button look and feel following Google Material Design Guidelines.

Created Xcode projects for all currently-built plugins.  Added Xcode workspace with "All" scheme for building GUI and all plugins.  Addressed some compiler warnings in plugin code.

On OS X, copy Rhythm-related files to the application bundle's Resources folder, and use the bundled copies at run time

Fixed: Changing data directory in GUI did not take effect if a recording had been started (and stopped) before. Only the first directory before the first recording was used. Fixed: EventBroadcaster was linking to Debug version of open-ephys.lib in Release mode

Fixed: Changing data directory in GUI did not take effect if a recording had been started (and stopped) before. Only the first directory before the first recording was used. Fixed: EventBroadcaster was linking to Debug version of open-ephys.lib in Release mode

- Also, changed Clock divider level: label to Clock divide ratio:
- Also, clock divide settings are now serialized to the configuration
  XML during a settings save.

- Sync signal, wired to BNC out with the update rhd2000.bit, can be set
  to a multiple of the sample clk period using the RHD2000Editor
- This commit corresponds to this pull request:
  https://github.com/open-ephys/rhythm/pull/11