Initial documentation revisions

Added scoping information, notes about init & data sharing
limitations and clarifications
Response to CR
Fix some pylint stuff to get the build to pass.
Response to CR
Merge pull request #179 from edx/flowerhack/revised-docs

Flowerhack/revised docs
revising workbench chrome/styling:

* to avoid workbench styles that club basic xblock UI rendering
* to be class selector-based
* to be namespaced to 'workbench'

TIM-211
Merge pull request #189 from edx/talbs/fix-workbench-chrome

XBlock Workbench Chrome Revisions