Publish several plugins, bump versions, update READMEs

org.chromium.identity
org.chromium.notifications
org.chromium.polyfill.xhr_features
org.chromium.socket
org.chromium.syncfilesystem
Remove all plugins that are already published and used as submodules
Remove inapppurchase plugin

Lived as a copy under:
PhoneGap-InAppPurchase-iOS

Id: cc.fovea.plugins.inapppurchase
Version: 3.1.0

Current version in the registry is 3.4.1
Remove chrome-cordova/plugins dir from search path

The plugin map was changed to list all plugin IDs in lower case. The registry
uses lower cases of all IDs.

Also published all plugins that weren't published before:

org.chromium.FileChooser
org.chromium.audioCapture
org.chromium.bootstrap
org.chromium.fileSystem
org.chromium.i18n
org.chromium.navigation
org.chromium.system.cpu
org.chromium.system.display
org.chromium.system.memory
org.chromium.system.network
org.chromium.videoCapture
org.chromium.system.storage