Revise cpp codes

Revise cpp codes

  - remove {} for single statement.
  - use noexcept keyword for non-throw methods.
  - use override keyword for overrided function.
  - remove unused methods.
  - use default keyword for empty destructors.
  - use explict keyword on single argument class constructor to prevent auto conversion.
  - use nullptr instead of NULL if possible.
  - use ! operator instead of comparing with false.
  - use auto when initializing with a cast to avoid duplicating the type name.
  - remove explict end return of void functions.

[Version] 0.5.19
[Issue Type] Refactoring

Change-Id: I5118a6ff5e85f9d9e02c7875b2cbe691652ef064