Fix forex

[goodboy]

Fixes to get fiat forex pairs working again on ib, since the volume / flows fsp work this stuff was broken since there is no vlm data provided on the feed but the code hadn't been adjusted to compensate. This patch set fixes that.

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Still todo:

• [x] fix x-axis labels back such that you can have only the price chart and you still see the label
• [x] on boot it seems the forex chart won't show currently until you hit r..
• ~[ ] maybe a default fsp for non-vlm feeds like these?~ leaving this for now, i'm sure someone will think of something.
• [x] still an issue with forex order mode stuff?, no all fixed now.

  (Pdb++) pp self._contracts
  {
  'eur.idealpro': Forex('EURCAD', conId=15016068, exchange='IDEALPRO', localSymbol='EUR.CAD', tradingClass='EUR.CAD'),
  'eurcad.idealpro': Forex('EURCAD', conId=15016068, exchange='IDEALPRO', localSymbol='EUR.CAD', tradingClass='EUR.CAD'),
  }

whereas the passed in symbol in this case is 'eur.forex', though the above is probably more correct?