Add Event Bus (#184)

Major internal refactor to use an event bus to pass event/messages along. These changes are largely invisible user facing but sets up internal design for real time stats and information.

- `--watch-config` logic refactored for events
- remove multiple SSE api endpoints, replaced with /api/events
- keep all functionality essentially the same
- UI/backend sync is in near real time now

go.sum

@@ -36,6 +36,8 @@ github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 h1:El6M4kTTCOh6aBiKaU
 github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510/go.mod h1:pupxD2MaaD3pAXIBCelhxNneeOaAeabZDe5s4K6zSpQ=
 github.com/json-iterator/go v1.1.12 h1:PV8peI4a0ysnczrg+LtxykD8LfKY9ML6u2jnxaEnrnM=
 github.com/json-iterator/go v1.1.12/go.mod h1:e30LSqwooZae/UwlEbR2852Gd8hjQvJoHmT4TnhNGBo=
+github.com/kelindar/event v1.5.2 h1:qtgssZqMh/QQMCIxlbx4wU3DoMHOrJXKdiZhphJ4YbY=
+github.com/kelindar/event v1.5.2/go.mod h1:UxWPQjWK8u0o9Z3ponm2mgREimM95hm26/M9z8F488Q=
 github.com/klauspost/cpuid/v2 v2.0.9/go.mod h1:FInQzS24/EEf25PyTYn52gqo7WaD8xa0213Md/qVLRg=
 github.com/klauspost/cpuid/v2 v2.2.7 h1:ZWSB3igEs+d0qvnxR/ZBzXVmxkgt8DdzP6m9pfuVLDM=
 github.com/klauspost/cpuid/v2 v2.2.7/go.mod h1:Lcz8mBdAVJIBVzewtcLocK12l3Y+JytZYpaMropDUws=