Fix compiler error from clang in C++11 mode

* ISO C++11 does not allow access declarations; use using declarations
  instead
Clean up octree_pointcloud_adjacency.h header

Changes include:

  * Fix style to comply PCL guidelines
  * Remove unused typedefs
  * Rearrange typedefs and using declarations
  * Strip trailing whitespaces
  * Reformat documentation comments
Fix 'undefined reference' linker errors

A simple program with the main function consisting only of one line:

pcl::octree::OctreePointCloudAdjacency<pcl::PointXYZRGBA> octree (0.5f);

will fail to be linked with a number of 'undefined reference' errors
like this:

    octree_pointcloud_adjacency.hpp:48: undefined reference to `pcl::octree::OctreePointCloud<pcl::PointXYZRGBA, pcl::octree::OctreePointCloudAdjacencyContainer<pcl::PointXYZRGBA, pcl::PointXYZRGBA>, pcl::octree::OctreeContainerEmpty, pcl::octree::OctreeBase<pcl::octree::OctreePointCloudAdjacencyContainer<pcl::PointXYZRGBA, pcl::PointXYZRGBA>, pcl::octree::OctreeContainerEmpty> >::OctreePointCloud(double)'

This commit adds an include that pulls in template definitions for the
Octree components, therefore allowing the compiler to instantiate
appropriate templates as needed.
Merge pull request #448 from taketwo/octree-pointcloud-adjacency

Bugfixes and clean-up in `OctreePointCloudAdjacency`