make Currency query the actual value of a pip

Until now Price objects always assumed a pip to be 0.001. Since we
display prices with a precision of 1/10th of a pip, we always displayed
four post-decimal positions.
With this change the actual value of a pip gets queried from the server
and used as expected. Examples for the different pip values include:

name            instrument pip
Gold/JPY        XAU_JPY    10
US SPX 500      SPX500_USD 0.1
UK 10Y Gilt     UK10YB_GBP 0.01
Copper          XCU_USD    0.0001

These values suggest that in some cases we will now get full precision
whereas in others we omit insignificant decimal positions that just
distract from the actual values.
MERGE W/ c96a2086
introduce EMA strategy
MERGE W/ c96a208621f2b96a56b4d1d620e9891183e71369
MERGE W/ c96a2086
MERGE W/ f21e8253
enhance EMA calculation
continue work