* Implement basic Lua output support
Ref #1700
Basic but working serialization to Lua tables.
* Escape larger set of characters in Lua output
Started with a minimum of replacements, this should be more complete,
tho not all substitutions are strictly required in Lua.
* Print simple keys unquoted in Lua output
String keys that satisfy the requirements for variable names can be used
as keys without quotes in tables.
* Quote Lua keywords in table keys
Keywords are not valid as unquoted keys, thus must be quoted
* Make output of unquoted Lua table keys optional
Generally safer and simpler to not do it.
* Hook up settings for Lua output
* Allow special characters in Lua prefix and suffix
--lua-suffix='});^M' didn't work, so taking this approach instead
* Panic on unhandled YAML Kind in Lua encoder
* Handle YAML case varied booleans in Lua encoder
* Handle special-case numbers in Lua encoder
* Reject unhandled scalar Tags in Lua encoder
* Add note about how Lua nil is unsuitable as table key
Could add some context tracking in the future to allow rejecting nil in
a table key context.
* Return error instead of panic in Lua encoder
* Add initial test for Lua encoder
Boilerplate mostly copied from toml_test.go
* Additional Lua output tests
* Generate Lua encoder documentation
Mostly just for the boilerplate
* Convert octal for Lua output
Lua doesn't have the 0oNNN syntax for octal integers, only decimal and
hexadecimal, hence those can be passed trough as is while octal needs
special treatment.
* Implement indentation in in Lua output
* Respect string Style in Lua encoder
Lua has 'single', "double" and [[ long ]] strings.
* Expand Lua examples
* Output line comments in Lua output
* Implement Lua globals output mode
* fix typo in a comment
* implement shell output format
* fix a typo
* add two test cases, have source uses ascii only
* add integration tests and documentation
* add fixes after code revieew
