* remote: move upload()/download() into tree
* remote: move path_info/path_cls into tree
* remote.azure: finish moving methods into tree
* remote.gs: finish moving methods into tree
* remote.hdfs: finish moving methods to tree
* remote.http: finish moving methods into tree
* remote.oss: finish moving methods into tree
* remote.s3: finish moving methods into tree
* remote.ssh: finish moving methods into tree
* remote.gdrive: finish moving methods into tree
* tests: update remote unit tests
* tests: update func tests
* remote: use walk_files() for all remotes
* list_cache_paths() now uses tree.walk_files() for all remotes except
local/ssh
* fix DS warnings
* bugfixes