Feature/grow - Merged master into #174

[stevencolinmartin]

Merged in current master to Grow feature.

Updates #174

[maximilianwulf]

Thank you, it has been imported.

[romainreignier]

Thank you @raghavakumar8 and @SteveQUT
This is exactly the feature I was missing.
Using addDataFrom was taking too much time to grow the GridMap.

I have successfully used this PR. It works and works fast.

About the API, for my use case, I receive a new Position, if it is not inside the current GridMap, I need to grow it with a new length delta. Maybe we could provide a grow method that takes a position and a length delta and grows in the direction of that position?

[romainreignier]

I had to replace this line by this one to avoid alignment issues:

Suggested change

	length_ = length;
	length_ = (size_.cast<double>() * resolution_).matrix();

[romainreignier]

Taken from here:

grid_map/grid_map_core/src/GridMap.cpp

Line 57 in c23dcde

length_ = (size_.cast<double>() * resolution_).matrix();

[kam3k]

Would it make sense to add the complementary shrink(...) function?

I personally have a use case where I want to regularly adjust the size of the map to contain some minimum amount of information. For example, keeping the smallest map possible that contains some minimum amount of obstacles. Here, it would be useful to grow the map when it is too sparse and shrink it if it is too dense.