JS parser: GWT parser copied

 Author:    Alexey Tsvetkov <alexey.tsvetkov@jetbrains.com>
JS parser: renamed imports of gwt ast to dart ast

 Author:    Alexey Tsvetkov <alexey.tsvetkov@jetbrains.com>
JS parser: removed GWT source info usage
JS parser: fixed expression statement stackoverflow error
JS parser: added NUMBER literal types

Splitted NUMBER literal type into NUMBER_INT and NUMBER_DOUBLE
JS parser: added insideFunction flag
JS parser: moved rhino parser to separate module
JS parser: removed magic string
JS parser: literals creation
JS parser: removed commented out code (source info usage)
JS parser: auto reformatted code
JS parser: made methods static where possible
JS parser: renamed sourceNameStub to comply with a codestyle (UPPERCASE)
JS parser: added description string to constructor arguments
JS backend: added jsCode test cases
JS backend: added jsCode definition
JS backend: expand jsCode at translator
JS backend minor: formatting