DOCS-1200 typo correction
split infinitive fix
DOCS-1201 clarifiy initialization of sharded cluster
DOCS-1140: sh.addTagRange() isn't cleaned up when dropping collections
DOCS-1163: clarification about padding factor section
explain.scanAndOrder available before 2.2

Removed introduction version from explain.scanAndOrder since available in 2.0.8 and perhaps earlier.

Signed-off-by: Sam Kleinman <samk@10gen.com>