Add update_account functionality

[grablair]

Adds update_account functionality. Supports updating the following global parameters:

• Account name
• Account type
• Account subtype
• Whether it should be included in net worth
• Whether it should be hidden from the account summary page
• Whether it should be hidden from budgets / reports

It also supports the following parameters only available on "manual" accounts:

• Account balance

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Tested locally on my own accounts.