[explore] in-place edit columns and metrics in data panle

[junlincc]

Proposed flow
1-1. Allow users to in-place edit metric setting - Metric name, Label, SQLExpression, Description, D3 format, additional info and to delete from a popover by double-clicking the metric's name from data panel.
1-2. Allow users to in-place edit column setting - Label, Description, Datetime format, is Temporal, is Filterable, is Dimension and to delete in a popover by double-clicking the column name from the data panel.
1-3 Allow users to in-place edit calculated column setting - SQL Expression, Label, Description, other format, is Temporal, is Filterable, is Dimension, and to delete the calculated column in a popover by double clicking the calculated column name from left data panel
3. Display sticky warning sign in popover
4. User receives a second warning message( # of users, charts, or dashboard might be affected by such action within team/the organization) before change/delete action is saved.

Design heavy project @mihir174