Gerrit Client: Use REST API to get server info

The Gerrit Client needs to know about some server configuration
parameters in order to render the UI and enable/disable certain
functionality. At the moment the information about the server
configuration is embedded into the host page, but there is a new REST
endpoint that exposes some of the configuration parameters, and it
should be used instead. Retrieving the data via REST is cleaner as
this is an API which can be also used by other clients. Also it
reduces some code duplication if the configuration parameters are only
exposed via REST and not once again via the host page.

This change is only a start to get rid of the configuration data which
is embedded in the host page. It only consumes those configuration
parameters via REST which are already exposed in the REST API. In
future changes the REST API should be extended to provide all
information that is needed by the Gerrit Client, so that no such data
must be embedded into the host page.

This change doesn't consume the download commands which are already
exposed via REST, since this requires quite some changes in the Gerrit
Client, and it is better done in an own change.

Change-Id: Id367ba82a29bfc8f84fa4bb3c2fc973355e5cc4a
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
18 files changed