Unify toolchain creation page so all happens in a single form

When I try to create a new version of a toolchain, such as: https://www.beat-eu.org/platform/toolchains/tutorial/full_lbphs/2 I can only see and edit the description of the toolchain, but the toolchain itself is not shown, and I cannot edit it.

The same applies, when a new toolchain is created.