use name internally instead of column
countvalues on non-columns
avoid quotes around scalar repr
expr shape doesn't rely on numpy
rename .name attribute on columns to ._name
test that reductions have _name
compute supports name -> _name change
server: name -> dataname, fix istabular to not isscalar
fix merge schema on single columns
isdatelike supports option types
datetime corrently returns _name
clean up api for name -> _name renaming
remove unused code
move nonzero, bool to Expr
replace iscolumn attribute with function
not iscolumn -> isinstance(schema, (Record, Tuple))
add exprsymbol
field class (replaces column)
test nested fields