Add hideModMail option

For user having an unused subreddit
Fix spelling
showImages: Ignore reddit.com for default module; fixes #1316

Regex also switched to use a non-capturing group.
settingsNavigation: Copyedit descriptions of options
console: Ensure that "Advanced options" text actually shows
css: Remove default margin attached to checkbox
console: Add spacing before label the right way
Merge pull request #1319 from mc10/advanced-options

Advanced options
Merge pull request #1318 from mc10/show-images

showImages: Ignore reddit.com for default module
Merge pull request #1317 from matheod/nomodmail

Add hideModMail option