Naming cleanup

closes #4069
- Rename everything from camelCase to lowercase + dashes
- Remove usage of `server`, `app` and `instance`
Validate and properly color letter count.

fixes #4087
- Adds correct validations for meta_title/meta_description
- Adds correct coloring of letter count
Fix minor IE UI issues

Closes #4088

- Fix Flexbox issue with the user list
- Fix positioning issue with the mobile menu toggle icon
- Make the mobile settings nav use absolute positioning (as fixed elements don't move inside a `transform: translate(...);` parent
Show all authors in post settings menu

Closes #4016
- Added 'limit=all' to API query to retrieve all users.
Merge pull request #4074 from halfdan/4069-rename

Naming cleanup
Add checks for packages and contentPath to startup

Refs #3864
- Make sure that require() is able to resolve all dependencies
  listed in package.json.  If packages are missing halt the
  bootstrap process and display an error and help message for user.
- Check that contentPath and its subdirectories exist with the correct
  permissions.
- Check sqlite3 database file is set for read/write access.
Merge pull request #4094 from frantzypants/issue-4016

Show all authors in post settings menu
Merge pull request #4089 from halfdan/4087-meta

Validate and properly color letter count.
Merge pull request #3913 from jaswilli/require-errors

Add checks for packages and contentPath to startup
Fix uncentered no posts view

Closes #4097
Merge pull request #4100 from novaugust/iss4097

Fix uncentered no posts view
Merge pull request #4090 from PaulAdamDavis/ie-fixes

IE UI fixes
Update meta_* helpers.

no ref
- Return meta_description based on post.html
- Return meta_description from post.meta_description if set
- Return meta_title either from post.title or post.meta_title if set
- Adds tests