remove all lib/libgit.py dependencies for command 'init'

+ replaces all libgit function with <git.cmd> executions
add remark for fixes
fix whitespace
save and use Repo().working_dir in ticket object
avoid unnecessary filename() call
replace find_root() with Repo().working_dir
replace find_git_repo() with Repo().git_dir
remove obsolete lib/repo.py