add datashape to sparksql type converter
spark: discover on pyspark rdds
resource on chunks passed kwargs

cc @chdoig
spark: into sparksql <- spark
spark: fix order dependent test
spark: SchemaRDD <- RDD
spark: sparksql_to_ds type converter
into: sparksql <- spark rdd
sparksql: discover
first draft of sparksql compute engine
sparksql: expand type coverage
sparksql: works with literals
into: clean up spark/sparksql into
sql: clean generation of summary by text
A variety of fixes for sparksql

1.  into list <- SchemaRDD turns Row objects to tuples
2.  IntegerType maps to int64, not int32
3.  Fixed sparksql imports
4.  post_compute on a head term calls collect
5.  into(object, RDD) uses list as intermediary rather than Iterable
    This is more widely supported
spark: clean up into ambiguities
discover(rdd) returns variable first dimension
try to avoid testing if no pyspark present

cc @cpcloud what is the best way to skip doctests with pytest?
sparksql: expand to binary operators and joins
into: df <- Projection(csv) respects names