JBIDE-15913 - Export dialogs should check the Android SDK

Introduces the MissingSDKStatusHandler that is triggered for undefined
SDK points. This is used by launch configurations and all the wizards
now.
align httpcomponent version	

align the httpcomponent.httpclient and httpcore version to 4.2.5 or
better.
Take caching into use for plugin infos

Start using the cached http client for retrieving the plugin infos.
Guard against unconfigured active engine

Adds a guard against missing active engine configuration.
update parent pom

Updates parent pom to 4.2.0.Beta1-SNAPSHOT
add direct dependency to httpclient4

refer to httpclient4 directly.