Dont use hardcoded version numbers in DB inserts

[MoralCode]

There are many places where augur writes a hardcoded version number to the database:

augur/augur/tasks/git/dependency_tasks/core.py

Line 129 in a60ddea

'tool_version': '0.89.1',

augur/augur/tasks/git/dependency_libyear_tasks/core.py

Line 55 in a60ddea

'tool_version': '0.44.3',

augur/augur/tasks/git/util/facade_worker/facade_worker/analyzecommit.py

Line 191 in a60ddea

'tool_version': '0.80',

augur/augur/tasks/github/pull_requests/commits_model/core.py

Line 68 in a60ddea

'tool_version': '0.41',

augur/augur/tasks/github/repo_info/core.py

Line 226 in a60ddea

'tool_version': '0.50.0',

... and many more.

some of these are clearly out of date. Others are so old that I suspect they may be referring to versions other than the augur core version.

For this issue: any of these that are supposed to refer to augur version numbers should import/read this value from metadata.py (and maybe it should move into the augur source tree)