modules/partdisks/front/glade: Semplice 6.0 ships with GTK+3.8, so lower the toolkit version limit.

A changed made some commits ago set the required GTK+ version to 3.10.
This condition is fullfied in Semplice 6.1+, but not in Semplice 6.0.
modules/partdisks/front/glade: ensure the mountpoint's entry_text_column is the one containing the description.

Due to some changes (???) we need to specify this manually (????).
6.1.1 hotfix.