Support for separate sink for error_logger messages

Forward port #292 to 3.x branch

Reviewed-by: shino

255 is a valid ISO-8859-1 character. This was fixed
on 2.x by #292. Forward port the fix into 3.x.

Function for printing stacktrace in human readable form

* Add formatting options to align text differently if desired
* Fix some typos in comments and docs
* Optionally print all metadata
* Fix R15 compatibility

Add option to format output with Width param in lager_default_formatter

ex:[{pid, ["123456:", pid], ["Unknown Pid"], {right, 10}}] -> if pid is in the metadata print "   123456:   <?.?.?>", otherwise print "nknown Pid"
placeholders: date, time, message, sev, metadata and new placeholder blank(blank | {blank, Fill} ignore width param

Fix several typos in srcs

Add option to print all metadata in the default formatter

Metadata can be printed with standard or custom internal seperators ad field
seperators. The defaults are "=" and " ":

  "key1=value1 key2=value2"

Fix R15 compatibility

Reviewed-by: mrallen1

Add test case and fix for #280

Reviewed-by: javajolt

This provokes the failure but I am having a hard time
capturing the failure. When run from the shell the
message {'gen_event_EXIT',Handler,Reason} is sent
but within the context of eunit it doesn't seem to be
going to the right mailbox.

Integrate patches into lager 3.0 release

Based on code review comments put this function into util.
Added a couple simple unit tests for sanity checking purposes.

Removed comment

During code review we decided that using Sink ++ '_lager_event'
would provide better isolation for gen_event names than
Sink ++ '_event' as we had been using up to this point.

For example a sink called 'audit' is now 'audit_lager_event'
than 'audit_event' which might clash with a user's predefined
own module or process name.

Add an unsafe_formatting code path

Reviewed-by: JeetKunDoug

Goldrush 0.1.7 provides for additional comparison operators in traces.

Previously bad configurations would be
silently ignored. Now they will throw
an error tuple.