Allow users to configure the Word Document Size for Import

Steps to reproduce

1. Create a blank page;
2. Go to [...] > Import Word Document
3. Import any word document of more than 20 MB

The import fails with the below error

The uncompressed size of your file is too large to import. You'll need to reduce the uncompressed file to 20MB or less

The below system property doesn't make any difference to import.

CATALINA_OPTS="-Dconfluence.word.import.maxsize=30"