Support for user-defined sophisticated page creators via plugins 

Whilst the built-in page creator (called via `posts new`) is likely sufficient for standard blog entries, it could be a great helper for some special post types, like photo publishing. E. g. when I publish the photo to my blog, I really want to run smth like `posts new_image ~/Images/Vacation/123456.jpg 'Crocodile eats my leg'` and yield the scaffolded markdown with link to image, an alternate text etc. Plus I want the original file to be resized to, say, 500px wide, watermarked, blackjacked and whored (and put to /media folder within all the thumbnails).

Or I may want to run `posts publish_new` to minimize FTP/SCP traffic.

To accomplish the task I have an amount of plugins, extending base `ruhoh posts` functionality, written. Now the problem is that the infrastructure is not ready to load those plugins within ruhoh executable. The patch below is to support plugins, having monkeypatched `Ruhoh::Resources::Pages::Client` with `Help_WHATEVER` const defined as well as respective methods.