Variables grouping fixes (#152)

- Grouping changes are detected and Grouped view is refreshed if
necessary
- Fixed problem with multiple entries of same variable in groups, when
user toggles between tabs and does not click save
- Couldn't open variable modal from grouped view, if revision was
greater than 1
Update Bootstrap to latest version, 3.3.0
Added workaround to nested modals scrolling issue that occurs in new BS versions
Merge branch 'master' of https://github.com/Tietoarkisto/metka