[SCB-538] Create SwaggerToClassGenerator

[wujimin]

preparing for create recursive dependency class

javassist can create normal dynamic class to classloader
but can not create recursive dependency dynamic class to classloader directly
to support recursive dependency, must save all class to byte[], and then convert to class

by SwaggerToClassGenerator we can do this in future PR

[coveralls]

Coverage increased (+0.02%) to 87.379% when pulling 590638a on wujimin:create-SwaggerToClassGenerator into 26cbe80 on apache:master.