Add remote method generator

[superkhau]

We should add the slc loopback:remote-method command to scaffold custom remote methods.

See #90

Subtasks

• First cut implementation
• Http mapping of arguments (see https://docs.strongloop.com/display/public/LB/Remote+methods?src=search&src=search#Remotemethods-HTTPmappingofinputarguments)
• Add isStatic
• Check input valid
• Add unit tests
• Either add a dummy method implementation to model js file or alternatively print instructions including dummy method code to the output after the JSON metadata was updated.
• Add http verb(major and custom)
• Make modelName an argument

[bajtos]

It would be good to land strongloop/loopback#1163 first.

[bajtos]

@jannyHou I moved the list of subtasks to issue description to keep them at the top.

[bajtos]

@jannyHou Nice start in #124! Please continue with adding tests for the new generator as it is implemented now before working on additional features.