featureless plugins on target platform cannot be installed by themselves - so build the TP from a feature + site.xml instead of .target file

Steps to reproduce:

1. download and unzip Eclipse JEE bundle (SR1 version or newer). The SR1 version includes this jsch plugin:

com.jcraft.jsch_0.1.41.v201101211617.jar

2. fire up Eclipse, then Window > Prefs > Install/Update > Available Sites > remove everything shown

3. Next, add these two sites:

• http://download.jboss.org/jbosstools/updates/target-platform_3.3.indigo.SR1-M/latest/ (JBoss Tools latest Target Platform)
• http://download.jboss.org/jbosstools/builds/staging/_composite_/core/trunk/ (JBoss Tools (Core) latest nightly build)

4. Click OK. Help > Install New > select the Core Trunk site (or "All Available Sites").

5. in the filter field, type "egit" and select the "JBoss Tools EGit Integration" feature. Click Next. Accept license and restart when prompted.

6. Now, in your installation, you'll see:

com.jcraft.jsch_0.1.41.v201101211617.jar
com.jcraft.jsch_0.1.44.v201101211721.jar

Problem here is that there's no way to install com.jcraft.jsch_0.1.44.v201101211721.jar without installing the component that depends on it. Apparently installing the thing you're about to build w/ PDE (despite the fact that we should all be building w/ m2e/Tycho) is bad even though the version you're about to build will be newer and therefore replace the installed one when you launch / install to test it.