CB-5063: Keep cordova.js in platform_www to avoid copying it from lib.

Currently all platform parsers (src/metadata/*_parser.js) copy
cordova.js from util.libDirectory for each run of prepare. This results
in errors when changing machines since the ~/.cordova/lib directory is
not populated.

With this change all the parsers construct the project www dir by first
copying contents of a new dir named platform_www (which contains
cordova.js) and then the www dir from the app.

Until individual platform create scripts will be updated to create the
platform_www dir, prepare.js checks if the platform_www exists and if
not, creates it using cordova.js from ~/.cordova/lib.

Even after the platform create scripts are updated the check will be
required for projects that were created using older version and don't
yet have a platform_www dir.

CB-5063: Keep cordova.js in platform_www to avoid copying it from lib.

Currently all platform parsers (src/metadata/*_parser.js) copy
cordova.js from util.libDirectory for each run of prepare. This results
in errors when changing machines since the ~/.cordova/lib directory is
not populated.

With this change all the parsers construct the project www dir by first
copying contents of a new dir named platform_www (which contains
cordova.js) and then the www dir from the app.

Until individual platform create scripts will be updated to create the
platform_www dir, prepare.js checks if the platform_www exists and if
not, creates it using cordova.js from ~/.cordova/lib.

Even after the platform create scripts are updated the check will be
required for projects that were created using older version and don't
yet have a platform_www dir.