Verb for adding dependencies to package.xml and CMakeLists.txt

Simple verb to add a package dependency to the 4 locations in a catkin package:

```
<run_depend></run_depend>
<build_depend></build_depend>
```

And to CMakeLists.txt

## Usage

```
roscd YOUR_PACKAGE_TO_MODIFY
catkin depend dep1 [dep2 [dep3...]]]
```

## Current Limitations

 - You don't mind loosing the blanks of your package.xml
 - You don't mind the deps being added to the bottom of package.xml
 - 'find_package(catkin REQUIRED COMPONENTS' must be on the same line

These are all pretty easy to fix, I just should be working on something else right now