added grouping to instance configuration UI

based on namespace prefixes - now each group has its own FIELDSET, which
makes it less chaotic

note that there's no explicit order yet - due to Ruby 1.9 hashes
retaining order and because the existing translations (DE and EN) just
happen to provide the right alphabetical order ("common", "languages",
"triplestore") - this should be easy to change later (patches welcome!)
simplified data structure
improve json serialization in hierarchical view

* now using jbuilder in view to render json
* fixes #192 (missing authorization check)
v4.1.1
add jbuilder to gemspec
remove heroku from gemfile

improved instructions on how to install heroku toolbelt
separate rake commands in travis script
dump jbuilder

it lead to strange recursive queries when rendering json for
hierarchical concepts, back to simple hash serialization
v4.1.2
fix collection type column values

looks like we forgot to migrate 'collection'-collection members when
refactoring collections
fix conversion to array

props to @mistydemeo for finding this one, fixes #233.
replace static bootstrap libs with bootstrap-sass
prefer sassy import statement over rails' require
tweak language selector positionings
remove comment remnants
suppress quick search

…until we have a less-crowded main navigation
fix button stylings
re-add some bootstrap js components to fix disfunctional navbar dropdown
merge branch 'bootstrap-sass'
handle bootstrap-sass in engine context