* Plugin callsigns, filechangehandler thread bug fix, plugin file perms

- Plugins are now assigned a callsign (a random string), which they use for all internal identification, like resource fetching and method calls. This is to ensure that plugins only access their own resources and methods.
- Made FileChangeHandler send off events to a queue, that is then consumed by the Loader, instead of calling import_plugin on its own, since that caused weird issues with the event loop and the thread watchdog is using.
- Plugins are now owned by root and have read-only permissions. This is handled automatically.

* Improved general look and feel of plugin tab

* Make all plugin entries have the same padding between them

* Make "No plugins installed" text look the same as "No new notifications"

Co-authored-by: WerWolv <werwolv98@gmail.com>

Fixed a bug where steam would sometimes fire message events on its own, causing them to be displayed as plugin titles.

Tile views will now run each in their own iframe. This makes it more safe as plugins no longer share the same javascript context, and plugin method calls can now be supported from the tile view.

* Initial commit. Untested

* various fixes

Core functionality confirmed working:
 - Iframe injection into steam client
 - Plugin fetching from the iframe
 - Plugin opening

* Added function to fetch resources from steam

* Improved injector module, added server-js communication

- Injector module now has methods for better lower-level manipulation of the tab debug websocket.
- Our "front-end" can now communicate with the manager (2-way), completely bypassing the chromium sandbox. This works via a dirty debug console trick, whoever wants to know how it works can take a look at the code.
- Added utility methods file, along with an implementation of the aiohttp client that our "front-end" can access, via the system described above.
- Added js implementations of the communication system described above, which can be imported by plugins.

* Added steam_resource endpoint

* Added basic installer script

* retry logic bug fix

* fixed library injection, event propagation, websocket handling

- library is injected directly into the plugins as well as the plugin list
- resolveMethodCall is implemented in the plugin_list.js file, which in turns calls window.sendMessage on the iframe to propagate the event
- websocket method calls are processed in their own tasks now, so as not to block on long-running calls.

Co-authored-by: tza <tza@hidden>
Co-authored-by: WerWolv <werwolv98@gmail.com>