* Now when we compile plugins it checks whether plugin's folder
  contains *.jucer file and appropriate Makefile for plugin in the
  Source/ folder.

* All modules are replaced with the JUCE 4.2.1 ones;
* Introjucer was replaced by Projucer;
* Also some appropriate needed fixes for Makefile.plugins;
* Removed -fvisibility=hidden flag for Linux building.

* 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 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.

- 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