MULE-7524: Encoded characters not working when using expressions for dynamic endpoints

_ Adding property getters in URIBuilder
_ Creating DynamicURIBuilder to create dynamic endpoint's URIs
_ Updating DynamicOutboundEndpoint to use a DynamicURIBuilder
_ Updating DynamicOutboundEndpoint creation on HttpProxy
_ Updating old tests that were using encoded mule expressions in the address's path
_ Updating migration guide
MULE-7524: Encoded characters not working when using expressions for dynamic endpoints

_ Applying changes after code review
Merge pull request #627 from mulesoft/MULE-7524

MULE-7524: Encoded characters not working when using expressions for dyn...