Allow configurable options for size limits when viewing files

Description

The limits on when a file will be displayed are hard coded. Would like to see options to configure this or adjust for specific files/environments.

Links / references

https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/models/blob_viewer/text.rb

self.max_size = 1.megabyte

Internal Zendesk: https://gitlab.zendesk.com/agent/tickets/86351