Add variable for intellij to disable/modify log output

[jan-vcapgemini]

As an intellij user I want to be able to disable/modify the log output of intellij.

When running intellij using ide intellij, intellij logs errors directly into the shell and clutters the console with it.

We need to add a new exported environment variable with which we can set intellij to log into a file or even completely disable its log output.

Might be required for #669 if we remove the background process.

[jan-vcapgemini]

If we remove the & from the intellij start script (e.g. in software/intellij/bin), we only get intellij debug output when using git bash. When using Windows Terminal it appears that the debug output gets omitted.
Adding > to the intellij start script does not suffice either because only one line gets logged not relevant to the current intellij process.