LMW-89 Preview image is now optional
LMW-85 Added requirements section
LMW-85 Add list of available widgets
LMW-85 Added auth widgets documentation pages
LMW-85 Changes from @juanferrub revision

https://github.com/liferay/liferay-screens/pull/46
Merge pull request #44 from liferay/LMW-89-ib-crash

LMW-89 Preview image is now optional
Merge pull request #45 from liferay/LMW-85-documentation-for-widgets

LMW-85 documentation for widgets
LMW-82 use computed properties instead of setter methods
LMW-82 use only one property
LMW-82 add base connector: it’s a task that could be queued and prioritized.
LMW-82 add login connector
LMW-82 apply connector to widget
LMW-82 add connector to signUp widget
LMW-82 add files to project
LMW-82 Connector attribute added to base class
LMW-82 Enum changed back to plain string because of compatibility with ObjC
LMW-82 Changed view class to protocol in login widget
LMW-82 Moved classes
LMW-82 Moved auth related widgets
LMW-82 Renamed folders to add Widget suffix