replace Observable.apply(rx.Observable) by toScalaObservable

and move Java types <=> Scala types conversions from
ImplicitFunctionConversions to JavaConversions
rename Observable constructors
add equals, hashCode, toString to Notifications
add Observable.from(Future) constructor
Manually merge branch 'master' of github.com:Netflix/RxJava into scala-constructors

Conflicts:
	language-adaptors/rxjava-scala/src/examples/scala/rx/lang/scala/examples/RxScalaDemo.scala
	language-adaptors/rxjava-scala/src/main/scala/rx/lang/scala/ImplicitFunctionConversions.scala
	language-adaptors/rxjava-scala/src/main/scala/rx/lang/scala/Observable.scala
Merge pull request #561 from samuelgruetter/scala-constructors

Creating Observables in Scala: Approach04