Added the ability to search query multiple fields at once
(cherry picked from commit 3295f29a2d0c84387fc39ce04d642c63b5c3a015)

Conflicts:
	src/test/java/redis/clients/johm/SearchTest.java
Seperated out NVPair class and merged with latest JOHm
(cherry picked from commit 9d2075628aa95479755bca1f64ee41a380714879)
Renamed NVPair to NVField
(cherry picked from commit 415737d3151839aa2577b2c28029489cda64cb33)
Improved handling of nulls
(cherry picked from commit 2b062483cf7d9f44575db2e7babc4c2c69e37375)