Injector API restructuring

Injector API:
- Removed socket connection
- Added dynamic API for injections (injection is allowed in all time
after Injector was injected)
- Debugger protocol is extensible now!

Added v8-debug dependence
(Small binary API what allow to extend debugger protocol)
The test "Cache messages when not connected" was removed and I did not find any alternative. I am wondering whether it is still needed to cache the messages?