Fix terms filter serialization of numeric terms

Serialization was being skipped when numeric terms were passed to terms
filter due to incorrect IsConditionless() logic.  This commit also fixes
a NRE that was being thrown when passing a null terms value.  An empty
filter is now created instead.

Closes #843.
Fix #860 GetMany() nullifies _index and _type
Bump version to 1.0.2
Merge tag '1.0.2'

1.0.2