Refactoring extension known / install codes. and NOW also support bitbucket.

Signed-off-by: Rack Lin <racklin@gmail.com>
Refactoring the Extensin\Hosting interface to Extension\Provider, Added `provider` key to extensions.json file, so every Provider should use the same file.

Signed-off-by: Rack Lin <racklin@gmail.com>
Added supports simple DSL extension name for `provider:user/package` and `provider@user/package` forms.

Signed-off-by: Rack Lin <racklin@gmail.com>
added unit-test for Extension Known.

Signed-off-by: Rack Lin <racklin@gmail.com>
Remove extensions.json and its associate methods temporarily.

Signed-off-by: Rack Lin <racklin@gmail.com>
Added detect extension name from config{0}.m4 and rename extracted source directory.

Signed-off-by: Rack Lin <racklin@gmail.com>
Remove unnecessary pass-by-reference signatures.

Signed-off-by: Rack Lin <racklin@gmail.com>
Merge pull request #402 from racklin/bitbucket

Refactoring extension known / install codes. and NOW also support bitbucket.