Sometimes amounts are exported with double minus to QIF

[rivaldi8]

Steps to reproduce the behaviour

• Create EUR accounts and transactions with an italian android version (keypad for amount only shows commas as decimal separator)
• Export as QIF
• Try to import to GnuCash desktop

Expected behaviour

Import process should proceed without problems

Actual behaviour

• Import process complains about QIF file format
• Some split transactions have double minus ("--") instead of single minus before the amount

Related to #655

Software specifications

• GnuCash Android version: 2.1.4
• System Android version: 5.1
• Device type: smartphone (moto G 4G - peregrine)

[rivaldi8]

Fixed by 2353957 in develop.

@codinguser I'm assuming here, as stated in Split's javadoc, that splits always have positive amounts. However, there are some places where it seems it allows negative amounts (example), which is confusing. If you could confirm that my assumption is right, I'll change all this code to assume positive amounts instead.

[codinguser]

@rivaldi8 yes, you are correct in your assumption.
Splits should always be positive, and the type determines the effect of the split.