adds cuke for work package type switching
keeps values when switching types
adds cuke for custom field behaviour on work package type switching
fixes custom_field_value permitance for params
refactors work package controller to always use work_package method
adapt specs
rewrote spec to improve readibility
use identical methods for ancestor/descendant fetching

Work packages use nested_set_now.
specs permissions for work_packages
Rails: Use 3.2.14 release instead of 3.2 git branch
MembersController: Fix Member being destroyed when editing roles

When removing all existing roles and adding a new role, the member was
destroyed before the new roles could be added. This might be the
result from a change in rails:
https://github.com/rails/rails/commit/c2362461cdf9615d5704d6f2942921b84b854c3c
Refactor Member and MemberRole: Disallow Member.destroy

MemberRoles can't be destroyed by themselves anymore, but Member must
be asked to do this. This allows Member to have control over validating
that each Member has at least one MemberRole and over deleting the Member
itself when no MemberRole is left.

An ugly piece of code makes MemberRole.destroy raise an Exception when
something tries to call it. This should prevent people from accidentally
using it.
Add tests for added Member role methods

Might not all work
Refactor member role management

Rename methods so they make clear whether they save and/or potentially destroy a member.
Fix member not being deleted when a user was removed from a group
Update changelog

[ci skip]
enables finding projects by identifier, scoped by visible
updates changelog
moved latest changelog entry out of version

[skip ci]
Merge pull request #278 from opf/feature/rails3_gem

Rails: Use 3.2.14 release instead of 3.2 git branch