[addons] replace OnEnable with event handlers for repository updater

[tamland]

No description provided.

[tamland]

jenkins build this please

[Rechi]

This causes a segmentation fault (on osx and linux) in the test suite.
I can look at it in greater detail later if needed.

[ksooo]

Crashes on Kodi exit.

(lldb) thread backtrace
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x8)
  * frame #0: 0x00000001003d8928 kodi.bin`CServiceManager::GetAddonMgr() [inlined] std::__1::unique_ptr >::get(this=0x0000000000000008) const at memory:2715
    frame #1: 0x00000001003d8918 kodi.bin`CServiceManager::GetAddonMgr(this=0x0000000000000000) at ServiceManager.cpp:176
    frame #2: 0x00000001003d2f53 kodi.bin`CServiceBroker::GetAddonMgr() at ServiceBroker.cpp:28
    frame #3: 0x000000010058a828 kodi.bin`ADDON::CRepositoryUpdater::~CRepositoryUpdater(this=0x0000000104b31850) at RepositoryUpdater.cpp:62
    frame #4: 0x0000000100589b35 kodi.bin`ADDON::CRepositoryUpdater::~CRepositoryUpdater(this=0x0000000104b31850) at RepositoryUpdater.cpp:61
    frame #5: 0x00007fffc3cd0178 libsystem_c.dylib`__cxa_finalize_ranges + 332
    frame #6: 0x00007fffc3cd04b2 libsystem_c.dylib`exit + 55
    frame #7: 0x00007fffc3c3b23c libdyld.dylib`start + 8

Seems it is not a good idea to have a global CRepositoryUpdater instance.