v0.1.2

Main changes:

• Supports timeunit option, including:
  • ns or nanosecond
  • us or microsecond
  • ms or millisecond
  • s or second
• Supports unsigned integer values
• Return {error, unauth} when authorization fails.
• Rename all pb modules prefixed with greptimedb_.
• Adds timeout settings for gRPC and gen_server:call.