Simplifying installation instructions by changing dependencies

[knmcguire]

There are a lot of ifs and buts when installing crazyswarm2. This draft PR is a suggestion to simplication.

What I've done is:

• Nice gui is optional now (as that is not installable as a pip package)
• Changed all tf-transformations to transform3d (that is a system package)
• Inputted all rowan functions to np.py backend (tested this with figure8 and it should work)
• Use rosdep to install dependencies

I also notice that rviz for the single line hello world didn't work anymore, which is because it's now defaulted to False, so here it is back on.

This should fix the following issues:

• fix Single segment trajectory failure #746 (since this is not used in the build system anyway)