Update git submodules
Update git submodules

* Update plugins/hooks from branch 'stable-2.15'
  to e51f704687f7aa44b448b5af62da3cabfab8a062
  - Merge branch 'stable-2.14' into stable-2.15
    
    * stable-2.14:
      More logging improvements to help tracking down hook problems
      Clarify usage of logging set-level command in documentation
      Update debug documentation to enable debugging for the whole package
    
    Change-Id: I9d345784c32e4c682ea8110af9323934d8c2ce52
    
  - More logging improvements to help tracking down hook problems
    
    Add more informational logs:
    
    - The configured hooks path.
    - The resolved path for each hook.
    
    Each of these is only logged once (the latter once per hook) so logging
    at info level will not be obtrusive.
    
    Log the path of the hook file if it does not exist. This is logged at
    debug level because it will be emitted on every attempt to execute the
    hook.
    
    Change-Id: I1fe6f860346d73648283178b58982180d2c35ce9
    
  - Clarify usage of logging set-level command in documentation
    
    The command only works for existing loggers. To set the level for
    all loggers one must change the log4j configuration.
    
    Change-Id: I44c04a2fcae8d8c9e812e7de28cf4ccfd3c31b65
    
  - Update debug documentation to enable debugging for the whole package
    
    Instead of only enabling for the HookTask class, enable for the whole
    hooks package.
    
    Change-Id: I33503f6185f07945f88b6de7a7aab4eaa509fbbf
    
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