Add option to remove app settings
Add option to remove app settings

Menu item "Reset app settings" now remove all the configurations/settings files related to app.
Previously it used to remove only window-state.json. This helps a bit in #310.

zulip/zulip-electron,zulip/zulip-desktop,zulip/zulip-desktop,zulip/zulip-electron,zulip/zulip-desktop,zulip/zulip-desktop,zulip/zulip-electron