Adding a test to check converters priority

Closes #876. When a converter B with more priority than A are
registered, vraptor is getting only the first converter,
ignoring priority.
Fixing converter priority

When a converter with more priority are registered, the DefaultConverters
override the current converter registered, allowing users to override
the interface Converter<Long> instead of override the LongConverter.
Testing converters with same priority
Improving docs
Adding more log messages and renaming objects
Adding more docs about behavior

And some information about people who have contributed with this class.
Getting back the cache
Fixing cache store when register a converter
Typo
Merge pull request #888 from garcia-jj/ot-gh876-converterspriority

Fixing alternatives with higher priority for converters