Resolves #33: Remove Boost, use C++11

[IanTheEngineer]

It may make sense to branch to melodic-devel prior to adding this commit.

• Replaced boost::trim with C++11 lambda implementation of string trimming
• Replaced all boost::shared_ptr with std::shared_ptr
  These changes were tested with all of the catkin tests provided, and passed.

[rhaschke]

I created a branch melodic-devel. Can you, please, re-submit this PR targeting melodic-devel?

[v4hn]

@rhaschke I retargeted the request. Github allows for that since a year or so ✨

This is overdue and should have been in kinetic already. Thanks @IanTheEngineer !
I proposed a minor change.

[v4hn]

I don't think this header should be in the public interface of the package.
I propose to either put it into an anonymous namespace in src/model.cpp (it's used only there atm)
or just move the file to src/ to avoid installing it.

[IanTheEngineer]

Agreed, this shouldn't be in the public interface. I'll move the file to the src/ directory as you and @rhaschke recommend.

[rhaschke]

... or just move the file to src/ to avoid installing it

I prefer this as it facilitates later reuse in another context.

[IanTheEngineer]

It appears I am mistaken on which license is required for code snippets from Stack Overflow. The whole discussion is rather heated and frankly, confusing, but it appears the license should be CC BY-SA 3.0. I believe BSD and CC are still compatible licenses, so I'll just update the license to CC.

[rhaschke]

Hi @IanTheEngineer,
I'm wondering why you want to get rid of boost::trim at all? I totally agree that it makes sense to switch from boost::pointers to std::pointers. However, why should we not re-use other boost utility functions? I don't see the point of inserting header-only code (like trim) all around, instead of using, well-maintained boost code, also header-only.
@v4hn, @davetcoleman What should be our policy regarding boost code?

[IanTheEngineer]

@rhaschke I don't have a particularly strong opinion on using boost::trim or not. The goal was just to use the tools afforded by C++11 where possible. These lambdas are pretty straightforward replacements for trim, but if we decide to leave boost as a build dependency just for trim, that's entirely acceptable.

[IanTheEngineer]

@rhaschke if things looks good, I can squash everything down into one commit.

[davetcoleman]

I agree boost is preferred over custom code, but should be replaced where possible by std

Thanks @IanTheEngineer !

[v4hn]

I think everyone agrees here already. If Boost offers functions that simplify our code base, then feel free to use them. There is no particular reason to remove them either, unless the standard offers equivalent solutions.