Refactored some amount methods into MonetaryFactory API, also used by
MonetaryAmounts singleton.
Removed template params from amount, keeping it on factory.
Merged comments.
Merge branch 'master' of https://github.com/JavaMoney/jsr354-api.git

Conflicts:
	src/main/java/javax/money/MonetaryAmount.java
	src/test/java/javax/money/MonetaryAmountsTest.java
	src/test/java/javax/money/impl/DefaultMonetaryAmountsSpi.java