ATLAS: update of `atlas-higgs-challenge-2014.xml`

* (addresses #660) (PR #730)
ATLAS: unified FIXMEs in Higgs challenge file

* (see PR #730)

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
terms: changes wording in T&C
UI: creates page for "Atlas Higgs Challenge 2014"

* (addresses #724)
terms: updated T&C

* updated “Terms of use” pointed by the legal service
templates: creates macro for home exp-dropdown

* creates macro for experiment dropdown button on the homepage
UI: fixes in collection-boxes