Fix file name and description generation in uploads

Set a proper time delimiter (:) in file generation and pad months, days,
hours and minutes equal to 9 with a 0.

Update the function for generating descriptions accordingly (also make
it support old incorrect file names).

Change-Id: I51cd99c7e07e19f406ace7c07bd015218e7cd937
Merge "Fix file name and description generation in uploads"