Read site settings from _config.yml

[woodpig07]

According to last week discussion, the way to read the jekyllpro-cms related settings will be changed in future release/version:

• schema files remain in _schemas/ folder.

• The .JekyllPro/config.json will be abandoned, instead, read languages from jekyll file _config.yml. i.e. /master/_config.yml

  # Build settings
  lang:
  - cn
  - en

• As a step in on-boarding wizard, generate initial schemas based on the collections in _config.yml (this one needs more design thoughts)

[woodpig07]

First and second items in above list have been done.