Added CompilerUtils.
ModuleManifestTask adds Build-Jdk to the manifest.
NbmPluginExtension now supports custom manifest entries.
Added getter for NbmManifest.
NbmManifest now supports storing any kind of entries (to support delayed evaluation of manifest entry values).
NbmManifest uses LinkedHashMap to preserve insert order.
Refactored ModuleManifestTask in order to prepare for adding up to date check.
ModuleManifestTask now actually considers custom manifest entries.
manifest generator task now hs an up-to-date check.
Workaround for now: NbmTask is never considered up to date because currently it considered itself up to date even if the jar changed (and who knows when). Not having up to date check is a minor loss of feature because nbm should be generated rarely and most likely as the last task, so it is reasonable to expect that it is not up to date.