Modified convert_data_to_integer and convert_data_to_float so that vector_end and missing values
are correctly handled for INT8 and INT16 types. Since vector_end is
(INT8_MIN+1) while missing is (INT8_MIN), check if the dereferenced
value is <= vector_end. If yes, handle as special case and return
INT32_MIN+1 or INT32_MIN.

Updated test case for checking bcf_*_missing values. Added line in vcf
and bcf files with missing values in many fields

Modified == operator in IndividualFieldValue and SharedField to handle
special floating point values (bcf_float_missing and
bcf_float_vector_end)
Merge pull request #258 from broadinstitute/intel_int_cast_missing_end_fix

Integer cast fix