Add logic to symlink promoted virtualbox artifacts
Use OMERO_JOB to generate default Ice 3.4 and virtualbox job names
Fix .ova name with new target
Review doc links creation to support new URLs

- Read the major version from the version number and append it to the product support link
Import re module
Exclude relative href links from http check
Refactor linkcheck logic in doc_generator

Forum URLs, e.g. http://www.openmicroscopy.org/community/viewforum.php?f=11
were not properly parsed by the current implementation. Replaced the
linkchecking logic using the one from SPhinx linkcheck.
Fix indentation
Fix url variable name
Remove optional argument from Request
Fix broken links condition
Allow to pass milestone by environment variable

Conflicts:
	omero-template.html
Merge pull request #16 from sbesson/rebased/master/virtualbox_fix_develop

Add logic to symlink promoted virtualbox artifacts (develop) (rebased onto master)
Merge pull request #17 from sbesson/rebased/master/doc_links

Review doc links creation to support new URLs (rebased onto master)
Merge pull request #18 from sbesson/doc_generator_fix

Doc generator fix
Merge pull request #19 from sbesson/milestone

Allow to pass milestone by environment variable