Item12661: Add support for recursive manifests in BuildContrib

BuildContrib supports MANIFEST files with the !include statement used when building Foswiki core. The MANIFEST file issues !include for each of the default extensions. The statement points to the Plugins or Contrib directory of each extension.

!include ../AutoViewTemplatePlugin/lib/Foswiki/Plugins/AutoViewTemplatePlugin
!include ../CompareRevisionsAddOn/lib/Foswiki/Contrib/CompareRevisionsAddOn

This task extends that to include MANIFEST files directly. In lib/Foswiki/Contrib/BuildContrib/BaseBuild.pm, alter the routine readManifest. If !include points to a file, recursively call readManifest() to process the file. Otherwise append the directory to the list of "other modules".

Purpose of this is to allow us to ship multiple versions of the TinyMCE editor, each with it's own manifest, instead of requiring one large merged MANIFEST.

Note that BuildContrib merges all individual MANIFEST files into a single manifest embedded into the _installer file.

-- GeorgeClark - 21 Nov 2013