DOCS-1455: Add Section to Describe dynamic TTL collections

Signed-off-by: Sam Kleinman <samk@10gen.com>
python: fixing kerberos link
DOCS-1455: edits
DOCS-1783: Backup documentation should cover need for journal files

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-1783: minor edits
DOCS-1708: Documentation isn't clear on what a 'blocking index build' is

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-1708: edits background indexes
datamodeling-reorg: initial breakup & restructure
DOCS-921: dm-reorg reorganizing & fixing up tocs

DOCS-921: dm-reorg moving intro and updating descriptive text