Fix error in documentation about currencyInformation

[thomaseizinger]

Currently, the documentation states the following about the currencyInformation object:

An object defining the conversion information to the currency of the associated nobt. If this object is present, the amounts of this expense are to be interpreted in the given currency. If this object is not present, it is assumed that the currency of this expense is equal to the currency of the nobt, hence the conversion rate is 1.

This is not correct.
The amounts listed in the shares are always in the currency of the nobt. The conversion information object represents the rate and the original currency. Clients can utilize this object to store information about the amounts that were entered by the user:

• the original currency
• the rate the client used to convert the entered amounts into the nobt currency