This commit is the start of the Editable Model work
for the planner, it creates a new delegate and shares
the code for the model that creates the gas types, so
we only need to change in one place to add new gases.
The table is already edition-enabled, but the outcome
is still undone, next commit - put all together.
Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>
