Avoid showing too many entries in the pie chart once.

When there are too many data entries, the pie chart is too crowded to
view. So we set a parameter in the class EchartsData called
maximumEntries, only the top <maximumEntries> will be shown and the rest
will be added to a single entry called 'other'.

Test: mannual tested.
Change-Id: I84bfadd3513c5827426d84ee7d5ad957b1ac5eab
1 file changed