Start and stop eviction worker threads based on demand.

Refs #1116
Fix an off by one in dynamic eviction threads.
Add nvd3 wtperf example to doc. #1147
Minor edits to wtperf doc page.
Merge branch 'develop' into dynamic-evict-workers

Conflicts:
	src/btree/bt_evict.c
	src/conn/conn_cache.c
	src/include/cache.h
Merge branch 'develop' into wtperf-doc
Move performance into its own section. #1147
Change to update-large-lsm run. #1147
Don't have eviction workers close sessions.
Merge branch 'develop' into dynamic-evict-workers
Lint
Add new chart and performance.dox.
minor review/wordsmithing.
update
Add large-lsm config and use that for wtperf doc.
Merge branch 'wtperf-doc' of github.com:wiredtiger/wiredtiger into wtperf-doc

Conflicts:
	src/docs/wtperf.dox
Fix inconsistent home dir naming.
Add descriptions of wtperf args and script options.
Merge pull request #1149 from wiredtiger/wtperf-doc

Add nvd3 wtperf example to doc. #1147
Fix up some oddness in the navigation of the documentation: there should be exactly one @subpage for each page, other references should use @ref.