update gradle-api artifact to version 1.6 this is required to make kotlin gradle plugin compatible with upcoming Gradle 2.0
cleanup Gradle API deprecation warnings to make plugin compatible with upcoming Gradle 2.0. This includes moving minimum compatible version from 1.4 to 1.6
Bug Fix: KT-4613

Fix replace with infix function intention to be inapplicable in the
case of package function calls, such as “kotlin.io.println(“”).”
Bug fix in intention to move lambda outside parentheses, handles commas better
Inspection to report negated binary expressions that can be simplified
Minor in JS backend: added useful message to assert(for EA-48931) and drop unnecessary code.
JS backend: added tests for infix calls.

 #KT-3998   in progress
 #EA-56241 in progress
JS backend: fixed infix calls.

#KT-3998   fixed
#EA-56241 fixed
JS backend: fixed compiler crash when use compareTo in infix call.

#EA-54661 fixed
Extract Function: Type parameters inference
Extract Function: Enable visibility selection when target container is class/object
Fix warnings
Fix containment check
Extract Function: Allow to combine throws with other exit points
Extract Function: Allow to select fragments which start with comment
Extract Function: Make member/top-level function private by default
Extract Function: Allow the user to proceed with extraction when non-critical errors are found
 #KT-4941 Fixed
Improve JetNameValidatorImpl performance
Fix message case in JetBundle.properties

Intention names should be lowercase, family names should have each word
except prepositions capitalized
Drop unused AnalyzerFacadeForEverything