#KT-2014 fixed

Fixed KT-2072: do not suggest to use type inference in Introduce Variable in case if expression type depends on expected type.

Replaced Usage of PathUtil.jarFileToVirtualFile() to PathUtil.jarFileOrDirectoryToVirtualFile(), removed the former.

 #KT-2001 fixed

 #KT-2001 fixed

added drop(n) and dropWhile(predicates) for KT-2067 - also tail() now returns the usual idea of tail() - namely everything but the head - rather than just the last element. Finally added more test sample code to the kdoc

In the most places in frontend identifier is stored in Name class, was in String.
Name has two advantages over String:
* validation: you cannot accidentally create identifier with dot, for example
* readability: if you see String, you don't now whether it is
  identifier, fq name, jvm class name or something else

Name's disadvantage is (small) performance overhead. We have no value types in JVM.

test should not fail if hash code or hash set is implemented diffently

TODO: uncomment assertions in LabelName constructor

% ./bin/kotlin -script hello.ktscript
hello world

% cat hello.ktscript
fun hello(what: String) = println("hello $what")
hello("world")

Note it currently takes 8 seconds to evaluate hello world script.

It is just prototype

* does not make top level symbols visible as class members yet
* does not take parameters
* Script class name is hardcoded now

http://confluence.jetbrains.net/display/~stepan.koltsov/REPL

This is important because test base classes like JetLiteFixture has
a lot of unused code/state that hardens reading/debugging.