fix Cmake deprecation warnings

[Jigoku]

Missing project(redeclipse);

CMake Warning (dev) in CMakeLists.txt:
  No project() command is present.  The top-level CMakeLists.txt file must
  contain a literal, direct call to the project() command.  Add a line of
  code such as

    project(ProjectName)

  near the top of the file, but after cmake_minimum_required().

Also for src/CMakeLists.txt and src/enet/CMakeLists.txt;

  CMake is pretending there is a "project(Project)" command on the first
  line.
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Deprecation Warning at CMakeLists.txt:1 (cmake_minimum_required):
  Compatibility with CMake < 2.8.12 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value or use a ...<max> suffix to tell
  CMake that the project does not need compatibility with older versions.

2.8.12 was released in 2013, seems logical to bump to this version for compatibility just to suppress these warnings.

[qreeves]

The CMake project is way out of date in other ways as well. There's another PR that's been left dangling by not responding to the review requests.