Fixes https://github.com/Particular/ServicePulse/issues/41
Fixed the assembly information to display the correct company name.
Fixed the Fatal error (exception) when trying to retry a failed message using id.
Added a "beta expired" message, closes #50
Renamed widget title, closes #43
Added custom checks screen
Added auto loading to custom checks.
Added placeholders when lists empty
mbiguous term "Last updated" for endpoint heartbeats, fixes #52
Added a retried tag to retried messages.
Fixes #53.