Make install-prereqs-ubuntu.sh work with newer versions of Ubuntu

[arthurbenemann]

Currently, the following setup pages both have something missing when trying to compile or simulate.
http://dev.ardupilot.com/wiki/building-px4-for-linux-with-make/
http://dev.ardupilot.com/wiki/setting-up-sitl-on-linux/

I tried to fix this by making the install-prereqs-ubuntu.sh correctly install everything that's needed. Here are the changes I did:

• Install libraries for 64bit Ubuntu systems.
• Less noise apt-get output
• Install packages required for SITL simulation
• Install pymavlink, MAVProxy and droneapi
• Remove modemmanager package
• Add Tools/autotest/ to the path
• Support for relative paths
• Install ARM toolchain at /opt

The script has been tested in a VM running a clean install of Ubuntu 14.04 LTS.

How to use it

The steps required for installing the environment are:
(please not that you will need to checkout my ubuntu_script branch while this PR is not merged)

# Install git
sudo apt-get -qq -y install git

# Clone the source
git clone https://github.com/diydrones/ardupilot.git

# Run the install-prereqs-ubuntu.sh script
ardupilot/Tools/scripts/install-prereqs-ubuntu.sh -y

# Reload the path (log-out and log-in to make permanent)
. ~/.profile

To build the code (e.g. AC for pixhawk):

# Build for ArduCopter
cd ~/ardupilot/ArduCopter
make configure
make px4-v2

To run a SITL simulation:

cd ~/ardupilot/ArduCopter
make configure
sim_vehicle.sh

[arthurbenemann]

arthurbenemann@284a18f
Added support for installing the project files at any path. For most users this will not change anything since they will be calling from the home directory.

The toolchain is now installed at /opt, leaving the user home directory more clean.

[tridge]

applied, thanks Arthur!

[arthurbenemann]

I'll update the wiki tomorrow.

[djnugent]

After running the script I had to install libc6-dev-i386 to actually get the code to compile on my computer. I was having errors with gcc-arm-none-ebai. Not sure why, thought I would share.

[arthurbenemann]

@djnugent We have the libc6-i386 package on line L13, maybe we should add the dev version as well. But I'm not sure what is the difference. I tested this in a clean Ubuntu 14.04 VM, and travis-CI builds it on Ubuntu 12.04 I think.

[djnugent]

Oh also running the script did not put sim_vehicle.sh in PATH. It never ran step 4 from the SITL setup guide. May have been an error on my end. Still trying to get situated with the development environment.

@arthurbenemann I am running Ubuntu 13.10 on a chromebook(CR-48). It had a weird install of Ubuntu. Probably a rare case.

edit: I assumed the script ran the entire setup. It looks like it only installs the proper software. My bad.