Added supplyCurve and demandCurve and use to find marketPrice of each skill.

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#	modified:   .cache
#	modified:   .worksheet/src/JobMarket.MarketTesting.scala
#	modified:   bin/JobMarket/MarketTesting.sc
#	modified:   src/JobMarket/Histogram.scala
#	modified:   src/JobMarket/JobSim.scala
#	modified:   src/JobMarket/MarketTesting.sc
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