Cleanup setup wizard. Split setup page into two.

First page is for giving server URL and advanced setup and second page
is for giving credentials. Second page will differ based on
authentication type supported by ownCloud server. For now only HTTP
credentials are supported.
Add and use credentials abstraction. Implement HTTP and dummy credentials.

To achieve that MirallConfigFile now exports several general
settings-related methods for subclasses (here: for HttpConfigFile), so
it does not have to contain any code targeted for specific
credentials.
Add Shibboleth credentials implementation.
Fix credentials handling in csync.

CSync module's properties can be set only after it was initialized, so
we split the sync context vfunc into two: the one ran before
initialization and the one ran before sync beginning.
Create HTTP credentials object for config without type value.
Remove unused stuff.
Move credential related files to creds directory.

CredentialStore is now only used for HTTP credentials, so it was moved
into http directory under creds.
Avoid a crash when disposing Shibboleth browser.
Make "Connect" button inactive until we get a Shibboleth cookie.
Fix displaying URL in account settings.

I deleted too much code there last time.
Fix copyright headers.
Move the creds/ and wizard/ directories one level higher.
Fix shibboleth syncing after client restart.

We needed to notify shibboleth-specific QNAM about new cookie and then
stop cramming that cookie into request via setHeader, but rather put
it to cookie jar and let Qt handle the cookie insertion into requests.
Fix build when using QtKeyChain.
Fix warnings.

Should be now compilable when run with -Wall -Wextra -Wpedantic
-Werror.
Fix warnings emitted by clang.
Make browser inside Shibboleth wizard page a bit larger.
Fill username in HTTP credentials setup page.
Fix indentation.
Split setup page into server and advanced parts.