Replaced InjectableBuilder with Injectable.build factory method
Added Provider class to serve as a base/ interface for other Providers, includes @build factory function
corrected implementation of Provider.
updated ConstantProvider to use Provider instead of ValueProvider
moved ValueProvider.ConstantProvider to Provider.ConstantProvider
moved ValueProvider to Provider.ValueProvider
Refactored FactoryProvider to use Provider as a parent class, removed FactoryProviderBuilder
moved ServiceProvider to Provider.ServiceProvider and removed ServiceProviderBuilder
removed legacy reference to InjectableBuilder