Merge pull request #456 from acramatte/NavbarCollapseFixedHeight

NavCollapse has fixed height on first collapse
Revert "Merge pull request #456 from acramatte/NavbarCollapseFixedHeight"

This reverts commit 265d3bf2659621e8ccba59dc7664c3b7a6623c24, reversing
changes made to 5088e747b3b228fac86a6b91d304303e00f3bdd1.
NavCollapse has fixed height on first collapse

- NavCollapse now uses the "nav_collapse collapse" class instead of
"nav_collapse" to fix the issue with a fixed height when collapsing the
first time.
- Removed data_target from Boostrap as it's already in Constants.

NavCollapse has fixed height on first collapse

- Fixed typo for "nav-collapse" (was "nav_collapse")
Merge remote-tracking branch 'upstream/master' into NavbarCollapseFixedHeight
Merge branch 'NavbarCollapseFixedHeight' of https://github.com/acramatte/gwt-bootstrap into NavbarCollapseFixedHeight