implement reply topic
implement reply_comment
added test doc
implement Git/Repository/Create
revised wrong schemas
implement modify comment / reply
reformat code
thread safe update (ensure update the correct document)
implement delete comment / reply
create Git repository when sign up
fixed wrong app.ini section name
Merge branch 'feature-git' into develop
Merge branch 'feature-discussion' into develop
Merge branch 'basic-testcase' into develop