Add helper functions for shared memory access to HTS files, indexes, and
iterators
Remove raw pointers from all Variant Readers and Iterators
- delete all copy constructors/assignment
- set all move constructors/assignment to default
- remove all nullptr assignments
Add move constructor/assignment tests for remaining Variant Readers and Iterators
Add explicit to constructors which can take a single argument
Refactored VariantReader initialization
Merge pull request #207 from broadinstitute/jt_raw_pointer_removal

Remove raw pointers from Variant Readers and Iterators