Not break when there are no plugins in the plugin dir

Fix for https://logstash.jira.com/browse/LOGSTASH-1324
Add remote option to wmi input.

based on code from https://logstash.jira.com/browse/LOGSTASH-1747
This allows any logstash instance to connect to WMI remotely.
Merge pull request #917 from electrical/change_pluginpath_error

Not break when there are no plugins in the plugin dir
Merge pull request #918 from electrical/wmi_remote

Add remote option to wmi input.
Remove 'monolithic' build targets (jar, etc).

This is to avoid users accidentally attempting to build the old
monolithic jar.

The change here is not a full purge of the old monolithic build but
just aims to remove the make interfaces which could attempt a monolithic
jar build.

I also removed some other stuff which should be unused.
Add test coverage for plain text fallback

This adds coverage for LOGSTASH-1595 as well (the binary blob test)
Make tests for LOGSTASH-1595 pass.
Add encoding and fallback coverage to json codec (LOGSTASH-1595)
Fix json encoding and callback tests (LOGSTASH-1595)
Merge pull request #919 from jordansissel/disable-old-monolithic-jar-builds

Remove 'monolithic' build targets (jar, etc).
Merge pull request #920 from jordansissel/LOGSTASH-1595

Add encoding and fallback test coverage to json and json_lines codecs
Patch aws-sdk's aws/core.rb to avoid failed autoloads.

This fixes LOGSTASH-1718.
Add test coverage for LOGSTASH-1718

This new test verifies that aws-sdk can autoload constants correctly.

I verified this test *fails* before the fix is applied and passes after
it is applied.
Merge pull request #923 from jordansissel/LOGSTASH-1718

Fix aws-sdk require problems.