Added HostId to CustomChecks and Heartbeats

Added new message to send when endpoint starts with Host information
Host info is now generated for < v4.4 endpoints as well. Also renamed the
startup message to RegisterEndpointStartup
Added tests and code for emmiting events when endpoints starts up
Added a sample project for the heartbeats
Making sure that pre v4.4 messages gets enriched with host info data if
the plugin is installed
Merge branch 'develop' into endpoint-instances
Making use of HostId
Merge branch 'develop' into endpoint-instances
Hack for SC assembly scanning for tests
There can be concurrency issues here.
Using HostId for all definitions
Merge pull request #196 from Particular/endpoint-instances

Adding host information to messages