Column width controllers

[andreypopp]

Currently column width is computed via functions in ColumnMetrics module. This code is also called by Header and Grid components to implement column resizing functionality.

Instead it would be useful to abstract column width computation and column resizing into a certain implementation of a column width controller. We can also provide the ability to replace a column controller by a different which implement a different strategy to managing column width.

That would also remove column resizing code from core and make core simpler.

To pass a column width controller to a grid one would use the following API:

<Grid columnWidthController={someController} />

if not columnWidthController is passed then Grid would use default implementation with the featureset closer to what the current Grid component provides regarding column width and column resizing.