Custom Card Pattern Fill Container

[Gentyspun]

Ref: #287

Changes custom card pattern to fill any container, and removes constraints from pattern

Steps to test:

1. Edit a post
2. Add a custom card pattern (Dark or Light, Brand has separate PR on the plugin)
3. Notice it fills the whole content area width
4. Add a column block and insert a custom card
5. Notice it fills the column
6. Save and check the same applies for the front end

Example: http://bigbite.im/v/HNQD6h