Add identifier to split points for automated vs user created split points

[ddanielr]

Is your feature request related to a problem? Please describe.
When split points are automatically created due to tablet sizes, these split points persist until a user runs a merge.
If a merge is run automatically, then it might remove split points that were purposely set by the user.

Describe the solution you'd like
Split points created automatically by accumulo should be identified as such so they can easily be removed.

[cshannon]

I will take a look at this issue, I think it makes sense to add a new column to track the split point type to the tablet metadata