Setting uploadfilelimit_x should be continous not selection

[NinaHerrmann]

Currently, the setting is a Drop Down - allowing only choosing between the defined upload limits.
However since e.g. 5-10GB is a rather large change it should be continous.

[bluetom]

This means the "Settings for the chunkuploader" - "Video size limit" option(s) in the Site-Administration settings of the block opencast.