Restructure installer to tuck EC stuff away somewhere else

 * Move all Encoding Converters merge modules to
     ExternalEncodingConverters folder
 * Remove some Perl and Python EC files from merge modules
     so that they get into main FW installer, and in main
     FW installation folder (instead of Common Files\SIL)

Change-Id: I55e087109431aafae5ab571742913011649bc92b