Document how plugins can react on changes in project.config

Change-Id: I6360a1ff7ac754a08dc21006a201e80473294003
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
Flush global plugin config on plugin reload

Global plugin configuration files are cached so that they don't need
to be parsed on every access. Flush the global plugin config from the
cache when the plugin is reloaded.

Change-Id: I0e37095f4e31f0cc87d0385f57abc8d6737ee221
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
Merge "Flush global plugin config on plugin reload"
Merge "Document how plugins can react on changes in project.config"