Make set of source packages for bootstrap-image configurable.

* Add new build profile 'minimum', which defines a minimum set of
  packages.
* Introduce HAIKU_BOOTSTRAP_SOURCES_PROFILE and let it default to
  '@minimum-raw'. This can be overruled in UserBuildConfig, setting
  it to '@release-raw' will cause all source packages required for a
  full release to be put onto the bootstrap-image.
* Add new image HaikuImageMinimum, which is meant to define the minimum
  useful Haiku image (yeah, I know that's vague).
* Add HAIKU_MINIMUM_BUILD, which indicates that HaikuImageMinimum should
  be used (it would be better to merge this with HAIKU_BOOTSTRAP_BUILD
  into something like HAIKU_BUILD_TYPE)
* Cleanup duplicate references to basic packages - those are now added
  by the topmost Jamfile (no longer referenced by the build profiles).

build/jam/RepositoryRules

@@ -1,5 +1,8 @@
 #pragma mark - Private
 
+# default value for the build profile that defines the set of source packages 
+# that will be put onto the bootstrap image
+HAIKU_BOOTSTRAP_SOURCES_PROFILE ?= @minimum-raw ;
 
 rule PackageFamily packageBaseName
 {
@@ -555,8 +558,8 @@ rule BuildHaikuPortsSourcePackageDirectory
 
 actions BuildHaikuPortsPackageList
 {
-	HAIKU_BOOTSTRAP_BUILD= $(JAM:E=jam) @release-raw build-package-list $(1) \
-		$(HAIKU_REPOSITORY_BUILD_ADDITIONAL_PACKAGES)
+	HAIKU_BOOTSTRAP_BUILD= $(JAM:E=jam) $(HAIKU_BOOTSTRAP_SOURCES_PROFILE) \
+		build-package-list $(1) $(HAIKU_REPOSITORY_BUILD_ADDITIONAL_PACKAGES)
 }