Only the main include should be used

https://gitlab.com/accounts-sso/libaccounts-glib/-/blob/master/libaccounts-glib/ag-account-service.h\#L30

This can be simplified once libaccounts-glib offers some options to
disable all non essential build features.

Increment also the library version, since new APIs have been added.

Modern compilers warn about using 0 instead of nullptr for pointers.

There's no need to use the latest devel image anymore.

Service types can have descriptions, but the Qt api doesn't currently allow to get them.
This commit adds a new description() method in the ServiceType class.

A test case with the new method has also been added.

Services can have descriptions, but the Qt api doesn't currently allow
to get them. This commit adds a new description() method in the Service
class. A test case with the new method has also been added.

Also wrap Application::supportsService()

Since this library is just a thin wrapper around libaccounts-glib, it
makes little sense to have debug messages in here: debugging can be
activated on libaccounts-glib, if needed.

With Qt5, we can use the .qmake.conf file to store the location of the
build tree.

Remove include file, use QSignalSpy whenever possible, align coding
style.

This generates a file that contains a strings like

  if("${PACKAGE_VERSION}" VERSION_LESS "${PACKAGE_FIND_VERSION}" )

instead of

  if(${PACKAGE_VERSION} VERSION_LESS ${PACKAGE_FIND_VERSION} )

and therefore work also if PACKAGE_FIND_VERSION is not defined, i.e. if
the user wants to find the package without specifying the version, i.e.

  find_package(AccountsQt5)

Without the quotation marks, this generates an "Unknown arguments
specified" fatal error.

Add const &
Some QLatin1String -> QStringLiteral
Do not ignore .arg() result
call reserve() with known list length

clazy: https://quickgit.kde.org/?p=clazy.git

The "use-dbus" is a boolean g_object property, with actual type of
gboolean, and gboolean is typedef int. g_object_get is a variadic
function (no static type checking), and stores the queried value
through pointer-to-int. If sizeof(bool) happens to be less than
sizeof(int) and the stack variable useDBus is packed tightly,
this can lead to stack corruption.

Compiling the lib with -fstack-protector immediately pointed out
the problem.

This caused a GCC warning when in pedantic mode.

Fixes: https://code.google.com/p/accounts-sso/issues/detail?id=239

Tests can now be run with a command like:

make check WRAPPER="valgrind --leak-check=full"

Expose the libaccounts-glib's "no-dbus" API as a constructor parameter
in Accounts::Manager.

The Application, Service and ServiceType classes already implement this
check. For some reason it was just missing in the Provider class.

Add Qt bindings for the ag_provider_get_domains_regex() method.