Initial commit
Add initial package.xml
plugins: Initial import px4flow.

Import px4flow plugin written by M.H.Kabir.
node: Initial import gcs_image_bridge.

In addition to `gcs_bridge` functions it sends imeges to GCS.
QGC receive it, but it constantly log this error:

    src/uas/UAS.cc 2093 Loading data from image buffer failed!
plugin: Add image_pub plugin.

TODO: image decode and publish.
Find why mavconn hangs on high speed io.
px4flow: Add send support.

Fix #1.
gcs_image_bridge: Preallocate image buffer (optimization)
px4flow: Update doc.
image_pub: Complete image decoding & publish.

Fix #3.
launch: Add px4flow.launch.

Now it has all features of px-ros-pkg (with some additions).
Update readme
save changes before moving, #101
move mavros to subdirectory, #101
move exras to subdirectory, #101
Merge remote-tracking branch 'mavros/master'

* mavros/master: (275 commits)
  move mavros to subdirectory, #101
  save changes before moving, #101
  plugins: setpoint: Update setpoint message name.
  plugin: setpoint_attitude: Update message name.
  Add link to ros-*-mavlink package wiki page.
  plugin: gps: Fix gcc 4.6 build (atomic).
  plugin: sys_status: Implement PX4 mode decoding.
  plugin: gps: Add EPH & EPV to diagnostic.
  plugin: gps: Move message processing to individual handlers.
  plugin: rc_io: Replace override service with topic. (ROS API change).
  Add dialect selection notes
  plugins: Change severity for param & wp done messages.
  plugins: Store raw autopilot & mav type values.
  plugins: init ctor (coverity)
  plugin: imu_pub: Add ATTITUDE_QUATERNION support.
  scriptis: mavcmd: Spelling
  scripits: Add mavcmd tool
  Add links to mavros_extras
  param: sys_status: Option to disable diagnostics (except heartbeat)
  plugin: command: Add takeoff and land aliases.
  ...
Add package index readme, Fix #101