As a Bamboo administrator, I want to be able to filter out warnings in the System Error logs

Background
Currently every time that Bamboo cannot connect to a branch (either branch was deleted or because of a connectivity issue) we log an error in the system logs. Build Engineering reported this is a pain point for them, as these events occur so often that they pollute the logs.
As they are logged under a section called "System Errors" and repetitive, they are misleading to users.

Bamboo logs show:

ERROR [11-BranchDetectionBackgroundThread:pool-19-thread-1] [BranchDetectionServiceImpl] Repository error while detecting branches for plan BUILD-PLAN

INFO [10-BAM::PlanExec:pool-17-thread-1] [DefaultErrorHandler] Recording an error: Plan 'BUILD-X8' detected that the repository is invalid. The plan will be disabled. : BUILD-X8

The message is generated even if the Automatic Branch Management is set to delete Deleted Branches.

Note:
As we will be improving the detection of branches deleted, the impact of this issue will be mitigated.

Proposed Solution:
Add some filter in the system errors section.