Make Event Logs More Searchable

[drieJAC]

Background
We have event logs which map the actions performed on various database entities and log warnings/errors but the logs are very basic. For this reason they're not so useful and rarely used.
If we add some search functionality they could become more useful in viewing an entity's timeline. This could be useful for developers to track down bugs but also for admins.

User Story
As a developer/administrator I want to be able to search/filter the event log for the following:

• candidate
• exercise
• application

To:

• filter by type of event - e.g. status change; email send etc
• search by id

We could also hook the error/warning logs into specific catch blocks for monitoring purposes, allowing us to see over time if certain errors are being thrown