Added /index handlers. (refs #2561)
Added status.json handler. (refs #2561)
Merge branch '2449-keep-write-blocks' into 2449-keep-index-status-handlers

Conflicts:
	services/keep/keep.go
Write status output in JSON. (refs #2561)
Merge branch '2449-keep-write-blocks' into 2449-keep-index-status-handlers
Merge branch 'master' into 2449-keep-index-status-handlers
Merge branch '2449-keep-write-blocks' into 2449-keep-index-status-handlers
Fix nil map bug and status.json route. (refs #2561)
Merge branch '2449-keep-write-blocks' into 2449-keep-index-status-handlers
Simplify GetNodeStatus to return only disk usage stats for volumes (refs #2561)

GetNodeStatus now only collects volume mount point, bytes free and bytes used.
More stats will be added as we find them necessary.
Merge branch '2449-keep-write-blocks' into 2449-keep-index-status-handlers
Added rudimentary GetNodeStatus test. (refs #2561)

Added GetNodeStatus unit test.
Revised structure of NodeStatus struct to reflect the desired output format.
Merge branch 'master' into 2449-keep-index-status-handlers
Added IsValidLocator to filter /index output.

IndexHandler should skip metadata files and anything else that isn't a
valid locator, so call IsValidLocator before including the file in the
index output. Refs #2561.
Add a device_num field to status.json output.

Include the underlying device number (as returned by stat(2)) in
status.json output, so clients can see if two Keep directories are
located on the same underlying volume. Refs #2561.
Merge branch 'master' into 2449-keep-index-status-handlers
Check that specified Keep volumes actually exist.

Incorporates code review for #2449. Refs #2561.
Merge branch '2449-keep-index-status-handlers'

Closes #2449, closes #2603, closes #2561.