documentation: improved markup in --print-databases section

Use `` for property names, mark "syncevolution <config>" as a
preformatted text block.

README.rst

@@ -295,24 +295,24 @@ backend. This works without existing configurations. However, some
 backends, like for example the CalDAV backend, need additional
 information (like credentials or URL of a remote server). This
 additional information can be provided on the command line with
-property assignments (`username=...`) or in an existing configuration.
+property assignments (``username=...``) or in an existing configuration.
 
 When listing all databases of all active sources, the output starts
-with a heading that lists the values for the `backend` property which
+with a heading that lists the values for the ``backend`` property which
 select the backend, followed by the databases.  Each database has a
 name and a unique ID (in brackets). Typically both can be used as
 value of the 'database' property. One database might be marked as
-`default`. It will be used when `database` is not set explicitly.
+``default``. It will be used when ``database`` is not set explicitly.
 
-When selecting an existing source configuration or specifying the `backend`
+When selecting an existing source configuration or specifying the ``backend``
 property on the command line, only the databases for that backend
 are listed and the initial line shows how that backend was selected
 (<config>/<source> resp. backend value).
 
 Some backends do not support listing of databases. For example, the
 file backend synchronizes directories with one file per item and
-always needs an explicit `database` configuration because it cannot guess
-which directory it is meant to use.
+always needs an explicit ``database`` property because it cannot guess
+which directory it is meant to use. ::
 
    syncevolution <config>