Pages should allow longer content

[ColdHeat]

Pages currently use a regular text type for the content column. This can lead to some users running into issues when they try to insert large HTML documents. The intention of the Pages feature isn't for arbitrarily large content but I do think we should be able to support most use cases that aren't abusive.

We should either tell the user that their content is too long or consider bumping up the size of the content column. Potentially to mediumtext.

https://stackoverflow.com/questions/13932750/tinytext-text-mediumtext-and-longtext-maximum-storage-sizes