Handle both legacy and current @type values in forward messages #119

Currently, agency expects and uses legacy @type attribute for forward messages:

did:sov:BzCbsNYhMrjHiqZDTUASHg;spec/routing/1.0/forward

However, as per aries spec (see here), a different value should be used for the attribute:

https://didcomm.org/routing/1.0/forward

Agency should support both formats for some time in order to remain backwards compatible.

Analogous change was already implemented in aries-vcx (see here).