[453276] Editing, publishing, versioning solution for documentation

A "org.eclipse.umlgen.doc" is contributed to define the doc entry point
"UML Generators Documentation" where each generator will add their TOC.
An EMF Compare library (org.eclipse.emf.compare.gendoc) is nested in
this plug-in (waiting for a released version) to manage the generation
of HTML files from wiki during the build of each generator. This library
was specifically adapted to manage anchors, see [453214].

Bug: 453276
Signed-off-by: Cedric Notot <cedric.notot@obeo.fr>
Feature naming and building of a new generator

- Homogenization of the features name (start with UMLGen). 
- Add of the Autojava generator in the global build.

Signed-off-by: Cedric Notot <cedric.notot@obeo.fr>
[438280] Happy checkstyle and formatter

- Checkstyle rules changed to authorize javadoc on types without
authors, to keep the same rule as the formatter for the order of the
imports (with static ones).
- Formatter rules changed to have spaces only instead of tabs.
- Line delimiters converted to UNIX for all files.
- Format applied on custom source code.

Bug: 438280
Signed-off-by: Cedric Notot <cedric.notot@obeo.fr>
[438003] Initial contribution changes (v3)

Cherry picking of the changes from the review of the initial
contribution (v3).

Bug: 438003