Add mount-point support

[mryznar17]

Add mount-point support requested in issue 45.
Added:

• MountPointPostProcessor which:
  • looks up mount-point labels in yang files
  • compares those labels with types taken from yangmntMappings
  • Adds types taken from yangmntMappings to definition containing mount-point label
  • If type has not been genereated (not specified in modulesToGenerate in Swaggergenerator), type is added as definition in swagger
• Extend SwaggerGenerator to execute MountPointPostProcessor when yangmntMappings are provided
• Extend Main.java do add CLI support:
  • I've tested solution with following cli command:
    java -jar .\cli\target\swagger-generator-cli-2.1.0-executable.jar -yang-dir './swagger-generator/src/test/resources/bug_45' -mount-point-mappings '{ \"list-entry-data\": [\"entry-type-1:content\",\"entry-type-2:content\"] }' -output 'output-swagger.yml' list-manager entry-type-1
• Extended README.md with instruction to the new mechanism
• Issue45:
  • Test solution