Allow setting FX rate for reports, e.g. set June 30th FX rate for reporting.

Allow setting FX rate for reports, e.g. set June 30th FX rate for reporting. I have to use both Navexa and Xero to cover all my needs. While Nevaea allows me to set FX rates for trades and income, it does not allow it to be set for reports. I have FX holdings, and when I generated 30 June reports to give an an accountant the values disagree with Xero reports as it uses a slightly different FX rate for June 30. Allowing me to set the reporting FX rate used on reports and portfolio views would allow consistent reports to be generated between Navexa and Xero