* docs - reorg pxf content, add multi-server, objstore content

* misc edits, SERVER not optional

* add server, remove creds from examples

* address comments from alexd

* most edits requested by david

* add Minio to table column name

* edits from review with pxf team (start)

* clear text credentials, reorg objstore cfg page

* remove steps with XXX placeholder

* add MapR to supported hadoop distro list

* more objstore config updates

* address objstore comments from alex

* one parquet data type mapping table, misc edits

* misc edits from david

* add mapr hadoop config step, misc edits

* fix formatting

* clarify copying libs for MapR

* fix pxf links on CREATE EXTERNAL TABLE page

* misc edits

* mapr paths may differ based on version in use

* misc edits, use full topic name

* update OSS book for pxf subnav restructure