Allow customization of available states

[mtotschnig]

• User might want to use cleared state for cash accounts
• User might want to not use reconciled state for bank accounts

[mtotschnig]

From user: Example of usage for cash accounts: i get recurring cash income (monthly) and also do pay some debts in cash recurringly, too (monthly). i add those transactions in advance to have an overview on how much money will probably be available for this month. currently i don't have an option to mark if the transaction actually occured. would be very neat to have like a box i could tick a checkmark on, when i actually received or paid the amount in question. like so i get a "cleared total' in addition to the total (reconciliation is not necessary but also an option).

Use case for bank accounts: i currently check my expenses against my online-banking - when everything is alright i set the transaction to 'cleared'. it is entirely unnecessary for me to take yet another step of reconciliation for my solely private purposes - a cleared total is enough for me, don't need an additional reconciled total.