Better sorting of comments and downtimes

This fixes a few things mainly adding the ability to sort the comments
and downtimes on the host and service pages. There were also a few style
changes I made as I saw fit along the way.

Mostly, the style changes were just wording tweaks, capitalization and
formatting. Added output to show current sorting method by default. This
may not be desired but I liked it so I kept it. Can remove it if people
do not like it.

Host comment sorting with sort method displayed:
![image](https://cloud.githubusercontent.com/assets/3237256/2633630/d3cec380-be70-11e3-9ef0-4080ae1906e3.png)

Service comments and downtime sorting with sort method displayed:

![image](https://cloud.githubusercontent.com/assets/3237256/2633641/f7cad152-be70-11e3-83d6-1b190a937de0.png)
![image](https://cloud.githubusercontent.com/assets/3237256/2633644/003b34b2-be71-11e3-99f1-6009a976ef25.png)

Downtimes page host portion with sort order displayed, fixed "downtime" to "downtimes" and capitalized "mark":
![image](https://cloud.githubusercontent.com/assets/3237256/2633655/2d1b1a6a-be71-11e3-952d-549f24edaa17.png)

Downtimes page service portion with sort order diplayed, fixed "downtime" to "downtimes" and added the "mark" line:
![image](https://cloud.githubusercontent.com/assets/3237256/2633664/4af04808-be71-11e3-9b72-f1b67a96a3c8.png)

Comments page host portion with sort order displayed:
![image](https://cloud.githubusercontent.com/assets/3237256/2633671/65900d74-be71-11e3-9d30-b53a8124064f.png)

Comments page service portion with sort order displayed and added the "mark" line:
![image](https://cloud.githubusercontent.com/assets/3237256/2633684/81f3fa20-be71-11e3-94fe-541d9f8163c3.png)