Improve gmail-filters

1. Read filters from a [google spreadsheet](https://docs.google.com/a/wealthsimple.com/spreadsheets/d/1YxQ6JWxxUNnjRYUNZ_Ij2_WjaBT_O1tmI3Bcz2YOVJM/edit#gid=0) rather than a static JSON file on github (easier for others to update)
1. Make filters more customizable. Now you can:
  - Add custom filter patterns (for example, I've added a few for Google Alerts, Github, etc)
  - Customize whether or not filters send skip the inbox even if they've been sent directly to you (by default, they will not skip inbox, but in certain cases they will, e.g. Github and Google Alerts)