Make it possible for installers to disable plugins by default.

Plugin manager reads Plugins/Ignored in installation global settings
now, and handles these plugins similar to as if they were experimental.

Change-Id: I56a0c5fe143e3fbd9261244bafece26d7b99c154
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@nokia.com>
Reviewed-by: Daniel Molkentin <daniel.molkentin@nokia.com>

src/libs/extensionsystem/pluginspec.cpp

@@ -275,6 +275,16 @@ bool PluginSpec::isExperimental() const
     return d->experimental;
 }
 
+/*!
+    Returns if the plugin is disabled by default.
+    This might be because the plugin is experimental, or because
+    the plugin manager's settings define it as disabled by default.
+*/
+bool PluginSpec::isDisabledByDefault() const
+{
+    return d->disabledByDefault;
+}
+
 /*!
     \fn bool PluginSpec::isEnabled() const
     Returns if the plugin is loaded at startup. True by default - the user can change it from the Plugin settings.
@@ -458,6 +468,8 @@ namespace {
 */
 PluginSpecPrivate::PluginSpecPrivate(PluginSpec *spec)
     :
+    experimental(false),
+    disabledByDefault(false),
     enabled(true),
     disabledIndirectly(false),
     plugin(0),
@@ -521,6 +533,11 @@ void PluginSpec::setEnabled(bool value)
     d->enabled = value;
 }
 
+void PluginSpec::setDisabledByDefault(bool value)
+{
+    d->disabledByDefault = value;
+}
+
 void PluginSpec::setDisabledIndirectly(bool value)
 {
     d->disabledIndirectly = value;
@@ -601,6 +618,7 @@ void PluginSpecPrivate::readPluginSpec(QXmlStreamReader &reader)
         reader.raiseError(msgInvalidFormat(PLUGIN_EXPERIMENTAL));
         return;
     }
+    disabledByDefault = experimental;
     enabled = !experimental;
     while (!reader.atEnd()) {
         reader.readNext();