Clean up main.go a bit
Clean up main.go a bit

* Don't call command_registry.FindCommand repeatedly
* Break a couple very long lines
* Remove os.Exit(1) that never could be reached: If the
  requirement.Execute call failed it would panic. The panic is
  recovered in main by the defer of handlePanics. handlePanics exits
  with 1 if there was something to recover.
* cmd -> cmdName in the case of it actually being a string, not a
  Command
* fc -> flagContext
* pluginsConfig -> pluginConfig

fujitsu-cf/cli,simonleung8/cli,cf-routing/cli,mcintyred/cli,mcintyred/cli,cf-routing/cli,fujitsu-cf/cli,markstgodard/cli,cf-routing/cli,evanfarrar/cli,simonleung8/cli,mcintyred/cli,hyenaspots/cli,hyenaspots/cli,markstgodard/cli,markstgodard/cli,hyenaspots/cli,markstgodard/cli,evanfarrar/cli,cf-routing/cli,evanfarrar/cli,evanfarrar/cli,mcintyred/cli,fujitsu-cf/cli,simonleung8/cli,hyenaspots/cli