move the log file viewer to its own plugin

We plan to have multiple different types of tabs.

raven/plugins/ravenlogplugin.py

@@ -8,6 +8,7 @@ from raven.pluginbase import PluginBase
 from raven.pluginregistry import PluginRegistry
 from raven.plugins.domain.menucontribution import MenuContribution
 from raven.plugins.domain.raction import RAction
+from raven.plugins.ravenlog.Tab import Tab
 
 
 class RavenLogPlugin(PluginBase):
@@ -29,9 +30,8 @@ class RavenLogPlugin(PluginBase):
     def current_file(self) -> Optional[str]:
         return self.main_window.tabs.current_file()
 
-    def create_tab(self, file: str):
-        self.main_window.tabs.create_tab(file)
-        PluginRegistry.execute("after_open_file", file)
+    def add_tab(self, tab: Tab):
+        self.main_window.tabs.add_tab(tab)
 
     def _action_about(self) -> RAction:
         about_action = RAction(