"Paste" application tweaks

Summary:
Tweaks to the paste app:

• I realized that unlike all the other apps, it makes more sense for the

default view of this one to be "create paste" instead of "list pastes" since
when you access the application directly you are most often wanting to share
something. Swap list out of the default slot and make edit the default.

• Make the textarea bigger (usability).
• Allow you to copy an existing paste.
• Implement 'raw view'.
• Tweak/adjust list view (usability, formatting).
• Tweak page titles.

Test Plan:
Created, copied, and listed pastes. Viewed raw paste. Created an invalid paste.
Tried to create a copy of a nonexistant paste.

Reviewed By: codeblock
Reviewers: codeblock, jungejason, aran, tuomaspelkonen
CC: aran, epriestley, codeblock
Differential Revision: 456