[flarectl] Adds User-Agent blocking to flarectl

[elithrar]

Adds the user-agents (shortname: ua) sub-command for managing User-Agent Blocking rules:

$ flarectl user-agents
NAME:
   flarectl user-agents - User-Agent blocking

USAGE:
   flarectl user-agents command [command options] [arguments...]

COMMANDS:
   list, l      List User-Agent blocks for a zone
   create, c    Create a User-Agent blocking rule
   update, u    Update an existing User-Agent block
   delete, d    Delete a User-Agent block
   help, h      Shows a list of commands or help for one command

OPTIONS:
   --help, -h   show help

Example:

ID                               Description                          Mode         Value                                                                                                                 Paused 
-------------------------------- ------------------------------------ ------------ --------------------------------------------------------------------------------------------------------------------- ------ 
62d49d9eacca445b9973f583688b74e7 Block the worst browser in the world block        Wawoo Browser 90210                                                                                                   false  
1ab4054cca55471387e407b35c6cc267 block IE6                            block        Mozilla/6.0 (osh; Intel Mac OS X 10_12_5) AppleWebKit/603.2.4 (KHTML, like Gecko) Version/10.1.1 Safari/603.2.4       false  
95ccf4e26e714d7c8e55d9a858258061 block IE6                            block        Mozilla/5.0 (osh; Intel Mac OS X 10_12_5) AppleWebKit/603.2.4 (KHTML, like Gecko) Version/10.1.1 Safari/603.2.4       false  
fdff66612b0a4d73ae72a0f13e7c6693 block IE6                            js_challenge Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_5) AppleWebKit/603.2.4 (KHTML, like Gecko) Version/10.1.1 Safari/603.2.4 false  

[elithrar]

Future work: improve the way we render table output.

[elithrar]

Fixed a bug on PUT requests where the id was not appended to the request URI.