elm: Remove elm app client/server implementation & APIs

elm: Remove elm app client/server implementation & APIs

This removes EO APIs related to an unmaintained client/server
model for applications. The reasons for this removal are the
following:
- unused
- no support in E
- relies on dbus as the sole transport layer
- unmaintained since the original patches
- only EO API (iow: beta, never released API)

I've also never seen the test cases (in elementary_test) actually
work.

According to Gustavo (k-s), the original author of this feature
is not involved in EFL at the moment, and unlikely to be in the
near future.

Note that terminology has in the past used those APIs when it
was still using some beta EO APIs. This code is now long gone,
removed in terminology commit 3ffcbadd6f9881472db6 (2014/12/13,
for version 0.8.0)

If someone wants to step in and maintain the implementation,
protocol and (EO) API, then feel free to revert this patch
and revive the feature. But it will need to be more solid than
this implementation.