[#116] handle negative values in bar chart
[#116] improve y min/max value handling
improve negative value handling in stackable chart
[#116] implement negative elastic Y handling
[#116] improve bar chart test cases for handling negative values
[#116] improve bar chart handling of mixed positive and negative values
[#116] improve line chart handling of mixed positive and negative values
[#116] implement line chart handling of mixed positive and negative values with stacking
added a simple indicator
added a simple indicator