Support cache configuration via Steampipe config

[kaidaguerre]

Allow setting cache enabled and TTL either via a global settings file

settings {
  cache = true
  cache_ttl = 600
}

or on a per-connection level via connection config:

connection "aws1" {
  plugin    = "aws"    
  cache   = true
  cache_ttl = 600
  profile     = "zaphod-aaa"
}