Fix checking of clipboard supported modes
Support make install
Add missing licence info to HaveSnippet
Update README
Update CHANGELOG
Remove paste services
Remove serial mode
Remove Qxt dependency
Fix typo
Certificate generation, QCA dependency

Bundled certificates were removed.
Make node a standalone entity, base for future work
Move network handling to ConnectionManager

ClipboardManager now manages only clipboard content and not
network connections/communication.
Implement peer verification, authentication

New verification system contains a wizard that will show
on one peer and prompt for security code on the other.

The security code is showed in the wizard and the user must enter
it on the other peer. If the code matches, the two peers are paired,
remembering each other's identity.

Certificate trust is no longer checked. The only thing that matters
is that peer has certificate that is in the local pool of authorized
nodes.

Conversations may now select required level of authentication, so that
introduction does not need any and clipboard sync does.

ConnectionManager exposes signals and slots for controlling
the peer verification in UIs.
Remove password

Password is no longer needed. Authentication is done by checking
certificates. Plain text communication is discouraged
and does not need password neither, as it is trivial to sniff it.
Auto discovery

Constants were moved to Version.h.
Remove deprecated utils
Remove deprecated conversation HistoryMixin
Fix compilator warnings
Remove clipboard unification
Do not crash if OpenSSL plugin for QCA is missing