- Introduced an internal boolean property 'overridable'
- Set this property to true while registering configuration
- Support inheriting this property from parent configuration node level

TextEditor.edit snippet overload now returns void. No longer preventing when already in snippet mode.

Fixes Microsoft/monaco-editor#320: Add workaround for Chrome v55 compositionupdate event being broken

- Contirbute parsing of config as an option to config watcher
- Introduce Config model to hold configurations , overrides and necessary data for services
- Refactor config services to use config models
- Add an api in config services to get configuration for a language