Add JSON loading to cursors and wt load utility. refs #740.

Allow set_key and set_value on JSON cursors.  The argument is a string
that is interpreted as JSON and must match the format created by a JSON
dump cursor or the 'wt dump -j' command.

Add -j option to 'wt load' utility to allow loading JSON.

Small adjustment to Python interface so that JSON cursor key/values inputs
are always treated as strings.

Added doc and Python tests for JSON cursors and wt load -j.
Fixed some 'const' compiler warnings.
Merge branch 'develop' into json-load
Fixed error in copying JSON with embedded Unicode.
Add tests for invalid Unicode in JSON.
Detect invalid Unicode during initial JSON scan when the error can be
accurately reported.
refs #740.
Changed JSON dump output format to add another level to 'tag' the data segment.
This makes JSON load parsing a little easier, and able to support some
differences in formats.  refs #740.
Simplify JSON load parsing and requirements further:
optional 'config', 'colgroups', 'indices' parts appear in any order,
and 'data' must be last.  refs #740.
Refactor, KNF, clean up.
Merge branch 'develop' into json-load
Fixed const correctness warnings.
Fix const correctness warning.
Fixed uninitialized var.
Fixed test error introduced by previous fixes.
Merge branch 'develop' into json-load
Code cleanup per agorrod's review, including putting JSON load utility
code in its own file.  refs #740.
Fixed compiler conversion warning.
Fixes for compiler warnings, cleanup as a result of running s_all.
refs #740.
Merge branch 'develop' into json-load
Fix warnings in util_load.
Merge branch 'develop' into json-load

Conflicts:
	dist/s_string.ok
	src/include/extern.h
	src/utilities/util_load.c
Merge pull request #1154 from wiredtiger/json-load

Add JSON loading to cursors and wt load utility. refs #740.