Added explicit dependency for plexus-component-metadata
Made iOsMobileProvision optional if iOsKeyId is specified

Since iOsMobileProvision isn't used if iOsKeyId is specified, moved the
check for a null iOsMobileProvision to after the logic run if an
iOsKeyId is defined.
App Updates set default keys for project

If an iOS or Android key is specified for an existing app a call will
be made to set the app's default keys to ensure they're built using
iOsKeyId or androidKeyId and not the key specified on the phonegap
build site.
Merge pull request #11 from kabroadb/master

Changes related to specifying correct iOS or Android key to use in build