Long load times for logs

[jack-ullery]

Describe the bug
The Logs tab usually takes a while to load (and refresh). This is because it calls journalctl every 5 seconds to parse all the system logs.

To Reproduce
Steps to reproduce the behavior:

1. Build and run AppAnvil
2. Click on the Logs tab on the top of the screen
3. Observe that it takes a significant amount of time for the logs to load

Expected behavior
The Logs tab should display some information relatively quickly, within a couple of seconds. We also don't need to refresh the entire cache of logs every few seconds. We only really need to check for the next set of logs, that might've been sent in the time since the last refresh.

Additional context
We could also parse the logs in batches. For example, we may be able to add logs in batches of 1,000.

[jack-ullery]

Solved with PR #30

[jack-ullery]

Further improvements with PR #41