Template intersections functions

It is my first attempt to template C++ functions so please review my code.
`planeWithPlaneIntersection` and `threePlanesIntersection` are now templated to allow usage with floats/doubles.

I also tested when using an Eclipse project; Eclipse still finds the functions definitions:
![eclipse](https://cloud.githubusercontent.com/assets/5566160/2729802/494ff2e6-c60f-11e3-83fe-44790b4fde8b.png)

Test unit is working (testing both floats/doubles behaviour); the output is :
```
./test/common/test_plane_intersection 
[==========] Running 3 tests from 1 test case.
[----------] Global test environment set-up.
[----------] 3 tests from PCL
[ RUN      ] PCL.lineWithLineIntersection
[       OK ] PCL.lineWithLineIntersection (0 ms)
[ RUN      ] PCL.planeWithPlaneIntersection
Plane A and Plane B are parallel
Plane A and Plane B are parallel

Plane A and Plane B are parallel
Plane A and Plane B are parallel

Plane A and Plane B are parallel
Plane A and Plane B are parallel

Plane A and Plane B are parallel
Plane A and Plane B are parallel

Plane A and Plane B are parallel
Plane A and Plane B are parallel

Plane A and Plane B are parallel
Plane A and Plane B are parallel

Plane A and Plane B are parallel
Plane A and Plane B are parallel

Plane A and Plane B are parallel
Plane A and Plane B are parallel

Plane A and Plane B are parallel
Plane A and Plane B are parallel

Plane A and Plane B are parallel
Plane A and Plane B are parallel

Plane A and Plane B are parallel
Plane A and Plane B are parallel

Plane A and Plane B are parallel
Plane A and Plane B are parallel


[       OK ] PCL.planeWithPlaneIntersection (1 ms)
[ RUN      ] PCL.threePlanesIntersection

At least two planes are parralel.
At least two planes are parralel.

At least two planes are parralel.
At least two planes are parralel.


[       OK ] PCL.threePlanesIntersection (0 ms)
[----------] 3 tests from PCL (1 ms total)

[----------] Global test environment tear-down
[==========] 3 tests from 1 test case ran. (1 ms total)
[  PASSED  ] 3 tests.
```