Added a configurations file in JSON format

# Added a Configuration file
Following a rule that I've extracted from 'the pragmatic programmer' book, I have added a configurations file
in JSON Format to the most of your component settings to make it easier to use.

__*Rule #6: Configure, don’t integrate*__
Details mess up our pristine code, they change frequently. Every change to the code is a risk to break the system. To avoid that, you should get the details out of the code, in configuration files. Configurable code is called « soft code », it’s adaptable to change.
Whenever you come to the point where you put details into your codebase, stop, and extract them out of it. The time you spend now will pay-off ten times in the future.

   - Added a configuration.json file
   - Added a manager singleton class to parse the file and return the settings stored in that file
   - Replaced some code to use the new singleton class (REConfigurationsManager.h)
   - Added a new category to manage hexadecimal color and convert them into UIColor
Can use 'light' and 'dark'