[doc] simplify mvn_artifact example with coordinates

webapp:webapp:war::3.1 and webapp:webapp:war:3.1 are identical from functional POV#
[doc] Update javapackages diagram
Fix XMvn configuration for native JNI repos

See: https://bugzilla.redhat.com/show_bug.cgi?id=1021608
[doc] Move sections in index.txt
[doc] Initial Ant section
[doc] Add Ant section to index
[doc] Add depmap section to index
[doc] Add comment to build section of Ant spec
[doc] Add section about depmaps

This will be probably removed, since it's implementation detail.
[doc] Add short section about xmvn-subst
[doc] Add mvn_artifact tip to Ant section
[doc] Add depmap section from index
[doc] Add docs outline