Fix fragments layout

[achilleas-k]

Fragments layout isn't working as intended on devices with large screens (tablets), where it should present a two-pane layout. This is a minor issue, and is mostly likely simply cosmetic, but it may cause undesirable behaviour when switching activities during a simulation run.

[achilleas-k]

Ended up reverting to the default classnames as generated by the new project template.
Will remain as it is now (no need to mess it up again unless we have to).