Store selected component in sketch.properties file

[codeanticode]

The default package name is processing.test.. Would be good to allow the user to set his or her desired package name when exporting the sketch as a signed app (and perhaps also an app name that includes spaces).

[codeanticode]

Use the existing sketch.properties file to avoid adding mode UI elements. Something like:

mode=Android
mode.id=processing.mode.android.AndroidMode
component=app
basePackage=com.appdev
version=1
prettyVersion=1.0

[codeanticode]

No need to store basePackage, version, and prettyVersion, as those can be edited in the manifest file.

Done with 3787f78 and 233ba02