Revert "Merge pull request #269 from finnishtransportagency/grouping-assets"

This reverts commit b35eeaabacc6b6fb243e1dde554c4e97d0d123ab, reversing
changes made to b7d79f64d31745da16b97dc3b45748004e8a62e1.
Disable `Tallenna` and `Peruuta` if no changes
Use `selectedAsset.isDirty` instead of custom fn
Mark selected asset as dirty upon creation
Merge pull request #270 from finnishtransportagency/disable_form_buttons_when_state_not_dirty

Disable `Tallenna` and `Peruuta` if no changes
Fix add new asset