Added github oauth api example
code style + cosmetic
Fixing tests-safe.ecf  (broken in last commit)
Fixing OAUTH_CUSTOM_API_20
which is intended to help consuming OAuth 2.0 api, without having predefined OAUTH_XYZ_API_20 as we have for google, and so on
Fixing compilation of *_CUSTOM_* classes
(note they are not yet tested, and were committed too early by mistake)
Refactor rename OAUTH API classes to follow the convention,
OAUTH_20, prefix.