Task :jagrDownload Logger errors

[Rdeisenroth]

When executing the new :jagrDownload task, the following errors appear in the log:

> Task :jagrDownload
Download https://github.com/sourcegrade/jagr/releases/download/v0.8.0/Jagr-0.8.0.jar
SLF4J: No SLF4J providers were found.
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See https://www.slf4j.org/codes.html#noProviders for further details.

[23-Jan.-31 13:41:16] [ERROR] - OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended

The intended functionality is still archieved but it is confusing some of the students even though it finishes the job.