[JAVASCRIPT] Error generating Javascript code when only some templates are present

[me717]

Description

Generating a javascript library does not find original template files if templateDir is set

Swagger-codegen version

2.2.1 (using the maven plugin)

Command line used for generation

swagger-codegen -l javascript -i swagger.json

Have primarily been using the maven plugin, but the above command produces similar output

Steps to reproduce

Run swagger-codegen with the language being 'javascript' and templateDir being set to a folder containing ApiClient.mustache, and no other template files

Suggest a Fix

In JavascriptClientCodegen.java, set the embeddedTemplateDir variable

[wing328]

Closed via #4585

Thanks for the contribution from @me717