Bugfixes et al: - don't throw a server error if one clicks submit on the empty form without specifying a file - allow to upload the same zipfile multiple times without throwing an error - streamline idioms
the max upload limit will now default to empty. Rationale: this value is one that ages quickly with respect to new storage requirements, and is currently set to something incompatible with the vanilla Naviserver configuration (500MB fs vs 20MB ns).
The upgrade script will make so that instances setting this parameter higher than the server upload limit configuration will be set empty as well (this would never have an effect, as server will prevent the upload altogheter anyway).
Max upload limit in bytes is now retrieved from a proc implementing this fallback to server configuration logics. Other than centralizing, its purpose is to be used in client-side code checks in the future so we could prevent a doomed upload in advance.