Set default visualization description to ''.
Return query with visualizations when saving.
Set Visualization.description to nullable.
Set description of default table visualization to "".
After duplicating a query, put user back on table tab.
There is no bar chart type -- it's column.
Add scatter plot type.

cc: @christophervalles
Make tooltip work for all chart types.
Fix for high charts bug with stacked areas.
Bring back logging level setting
Remove SERIES_TYPES from Visualization.
Performance improvements for chart rendering:

1. Don't redraw when adding or removing a single series, but redraw at the end.
2. Use $timeout to postpone high charts rendering until DOM is ready.
Merge pull request #86 from EverythingMe/fix_viz

Fixes and improvements (most related to visualizations)