Backend.ai

-------------------

- Drop custom-patched aiohttp and update it to official v3.3 release. (78)
- Fix intermittent failures in streaming uploads of small files.
- Fix an internal "infinity integer" representation to have correct 64-bit maximum
unsgined value.

-------------------

- Fix a regression bug when restarting kernels.

------------------

- Limit the default number of worker processes to avoid unnecessarily many workers in
many-core systems and database connection exhaustion errors (lablup/backend.ai17)
- Upgrade aiotools to v0.6.0 release.
- Ensure aiohttp's shutdown handlers to have access to databases during their
execution, by moving connection pool cleanups to the aiohttp's cleanup handler.

------------------

- Fix bugs in resolving image tags and aliases (71)

------------------

- Hotfix for handling of dotted image names when they are terminated.

------------------

- Hotfix for handling subdirectories in batch-mode file uploads.