Fixes the build deps between opentxs and opentxs-server.

Adds a COMPONENT name. Otherwise the build package would be called
opentxs-*-Unspecified. In the opentxs-server package a dependency is
defined on the opentxs package. There was no such package. This commit
lets opentxs-server reference opentxs-main (it had to have a suffix).

Note also https://github.com/Open-Transactions/opentxs-server/pull/29