What: Changes to support custom usage limit for the project. With this implementation by default project usage limit is taken from configuration flag. If project DB field usage_limit will be set to value larger than 0 it will become custom usage limit and we will be used to verify is limit was exceeded.
Whats changed:
usage_limit (bigint) field added to projects table (with migration)
things related to project usage moved from metainfo endpoint to project usage type
accounting.ProjectAccounting extended with GetProjectUsageLimits() method
Why: We need to have different usage limits per project. https://storjlabs.atlassian.net/browse/V3-1814
