More unit tests for block selection
Renamed Offset to Column

In an effort to get naming consistent in the APIs I chose to use Column
for position based calculation and Spaces for space based calculation.
This renames the existing Offset methods to Column to reflect this
Code refactoring

Moved the methods on ColumnWiseUtil onto a couple of other types.  Most
of the methods felt more natural on SnapshotLineUtil and
SnapshotPointUtil because they are line and point based queries.
Putting them there makes it easier to remember where to look for them
going forward.

The methods themselves weren't changed.  Just moved them around