Add CL platform enum to Xflow base.
Add multiplatform node support to Xflow.registerOperator.

* Operators are now indexed by platform.
* Platform can be defined using 'platform' attribute in operator data.
* If platform is not defined operator is registered as ordinary JS operator.
Add platform attribute to Xflow base to indicate current active platform.
Update Xflow.getOperator() to support multi-platform nodes
Add missing semicolons and curly brackets

Refactoring base.js.
Fix code indentation etc. to better follow JavaScript coding conventions

Refactoring Xflow base.js.
Improve comments

Added more comments in base.js and operator.js.
Merge pull request #41 from Cyberlightning/feature/xflow-multiplatform-operators

Feature/xflow multiplatform operators