Created strongly typed configuration class

[kant2002]

Created strongly typed configuration for the following purposes:

• Remove configuration parsing logic and defaults handling from the
  CDVViewController.m
• Improved testability of the Cordova configuration and other parts of
  code which related on configuration could be much clearly mocked.
• Reduction for code duplication during configuration parsing.
• Ability to verify configuration issues during parsing, For example
  passing not a number to the value which expected to be a number should
  result to warning, so application developer could easily find error on
  their side.
• Single place for storing configuration defaults.

Drawbacks in current implementation

• Not sure about memory leaks during such approach. Not very familiar
  with iOS. This is need review
• No tests so far, could be added later if whole idea get traction.
• Currently no support for settings with limited set of values allowed.
  Like «PaginationMode». Again could be added if whole idea would be
  supported.

[shazron]

Thanks but due to the pluggable webview feature, each WebView plugin has its own configuration now (4.0.x branch). This PR will be auto-closed.