Completed stuffs, improvements.

- Fixed mod/admin login issues.
- Fixed captcha issues and improved the code.
- Added file verification for WEBM, OGG, and MP3.
- Added a new site theme.
- Limited the maximum files per post by the MaxHttpRequest /
MaxFileSize.
- `adminaction.aspx` is now functional.
- Post editing for mods and admin is now supported.
- Added prettify to the project.
- Workaround a bug where a file can be swapped if uploaded at the same
time (due to files names being in a windows time stamp).
- Generic improvements.