Add asset management scripts

infra/bots/assets/README.md

+Assets
+======
+
+This directory contains tooling for managing assets used by the bots.  The
+primary entry point is assets.py, which allows a user to add, remove, upload,
+and download assets.
+
+Assets are stored in Google Storage, named for their version number.
+
+
+Individual Assets
+-----------------
+
+Each asset has its own subdirectory with the following contents:
+* VERSION:  The current version number of the asset.
+* download.py:  Convenience script for downloading the current version of the asset.
+* upload.py:  Convenience script for uploading a new version of the asset.
+* [optional] create.py:  Script which creates the asset, implemented by the user.
+* [optional] create\_and\_upload.py:  Convenience script which combines create.py with upload.py.
+
+
+Examples
+-------
+
+Add a new asset and upload an initial version.
+
+```
+$ infra/bots/assets/assets.py add myasset
+Add script to automate creation of this asset? (y/n) n

[stephana, 2016/06/15 13:57:30]

Can you update this example to include the new FYI information ? 

[borenet, 2016/06/15 14:31:27]

Done.

+$ infra/bots/assets/myasset/upload.py -t ${MY_ASSET_LOCATION}
+$ git commit
+```
+
+Add an asset whose creation can be automated.
+
+```
+$ infra/bots/assets/assets.py add myasset
+Add script to automate creation of this asset? (y/n) y
+$ vi infra/bots/assets/myasset/create.py
+(implement the create_asset function)
+$ infra/bots/assets/myasset/create_and_upload.py

[rmistry, 2016/06/15 13:47:18]

Nit: Do you need \_ here as well?
Also in create_asset and MY_ASSET_LOCATION above.

[borenet, 2016/06/15 14:31:27]

I don't think so, since it's in the quoted block.  It looked fine when I pasted
this into a markdown preview app.

+$ git commit
+```