[Processing] Remove print statements which sometimes cause an exception
[Processing] Add GRASS r.univar and update r.fillnulls
[Processing] Hide some OTB params under Advanced button and improve handling of advanced parameters
[Processing] Comment debuging statements in OTB which clutter up Processing log
[Processing] Add *.* file filter to batch processing input panel
Merge pull request #1512 from radosuav/small_processing_fixes_3

[Processing] Small fixes