BUMP 2.6.6
DOCS-4488: more tickets for the 2.6.6 release notes

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-4488: fix syntax for 2.6.6 release notes

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-3388: edits to release notes
DOCS-4192: clean up release texts
minor: whitespace cleanup
DOCS-4500: fix typo
DOCS-4499: fixing xref
DOCS-4498: fixing image width
improvements to findAndModify command ref