Changes

Automatically export memory.allocate (previously allocate_memory) so you don't have to.
Generate new SomeEntity.load(id) and someEntity.save() wrappers around the store API.
Various subgraph validations have been added to the CLI, including catching:
- invalid contract addresses,
- invalid ABI references,
- invalid or unsupported ABI files,
- events that are not present in the ABI,
- invalid field types in the GraphQL schema, and
- entity types with missing id fields.
  Most of these validations will show a list of possible solutions.
Support for new subgraph manifest fields has been added:
- description and repository at the top level,
- network (one of mainnet, ropsten, rinkeby, kovan, to be extended) at the data source level.
The AssemblyScript version has been bumped to the latest master.

Fixes

Bypass authentication if the system keychain cannot be accessed (useful for CI systems and other headless or non D-Bus systems).