Parameter type support

Adds support in the sandbox for parameters that utilize other input types other than text string. 

In this PR, I added support for the File type (addresses issue https://github.com/nelmio/NelmioApiDocBundle/issues/132) and boolean, but it is conceivable that this can be extended to add more support such as a dropdown select box for multiple choice and even extended to add validation support within the text box. 
why hardcoding the formats ?