remove Eclipse Webtools components from default installation

[martinlippert]

Remove these features from the default Spring Tools for Eclipse package:

• org.eclipse.m2e.wtp.feature
• org.eclipse.wst.server_ui.feature
• org.eclipse.wst.server_adapters.feature
• org.eclipse.jst.server_adapters.ext.feature
• org.eclipse.jst.server_adapters.feature

[martinlippert]

As a mitigation, we should provide a script that installs those components into an existing Spring Tools for Eclipse installation.