Merge remote-tracking branch 'stable/master' into HEAD

* stable/master:
  This is Tuleap 6.6.99.19
  LESS dev mode added and 'make less' modified (head limit)

Change-Id: I4bb06d4e9729142ae0797bed00995ad45cd033ad
Replace inclusion of bootstrap.css by bootstrap/*.less

- Add bootstrap/*.less files
- Remove bootstrap/stripes.less (icons)
- Move less target in a dedicated file
- Exclude bootstrap from less target
- Switch to bootstrap 2.3.2
- Merge less.sh and less-dev.sh to less.sh
- Switch to recess
- Cleaning common/style.less

Change-Id: I84dd1933503456674f3e2404d977c1d70b67e3b1
Merge remote-tracking branch 'gerrit/5283_use_less_mixins' into HEAD

* gerrit/5283_use_less_mixins:
  Replace inclusion of bootstrap.css by bootstrap/*.less

Change-Id: I4a1fce8bda9e48dd2c096f371c37b5e8f15823eb
This is Tuleap 6.6.99.24

Change-Id: I64e296d4761abf21b7d789fb72517d496b7f0126