CLI: change argument naming convention

As in all other Unix/POSIX tools and JVM language compilers, multiple words
comprising the argument name should be lowercase, separated by dashes

compiler/testData/cli/js/jsHelp.out

@@ -1,12 +1,12 @@
 Usage: kotlinc-js <options> <source files>
 where possible options include:
   -output <path>             Output file path
-  -libraryFiles <path[,]>    Path to zipped library sources or kotlin files separated by commas
-  -sourcemap                 Generate SourceMap
+  -library-files <path[,]>   Path to zipped library sources or kotlin files separated by commas
+  -source-map                Generate source map
   -target <version>          Generate JS files for specific ECMA version (only ECMA 5 is supported)
   -main {call,noCall}        Whether a main function should be called; default 'call' (main function will be auto detected)
-  -outputPrefix <path>       Path to file which will be added to the beginning of output file
-  -outputPostfix <path>      Path to file which will be added to the end of output file
+  -output-prefix <path>      Path to file which will be added to the beginning of output file
+  -output-postfix <path>     Path to file which will be added to the end of output file
   -tags                      Demarcate each compilation message (error, warning, etc) with an open and close tag
   -verbose                   Enable verbose logging output
   -version                   Display compiler version

compiler/testData/cli/js/outputPostfixFileNotFound.args

@@ -1,5 +1,5 @@
 $TESTDATA_DIR$/simple2js.kt
 -output
 $TEMP_DIR$/out.js
--outputPostfix
+-output-postfix
 not/existing/path

compiler/testData/cli/js/outputPrefixFileNotFound.args

@@ -1,5 +1,5 @@
 $TESTDATA_DIR$/simple2js.kt
 -output
 $TEMP_DIR$/out.js
--outputPrefix
+-output-prefix
 not/existing/path