Header files are not installed in standalone build

[Masaki Murooka]

Thank you for introducing the standalone build. @gergondet
In the standalone build of the MultiContactController (i.e., BWC dependent controller), the BWC header files are not found, can you please update to install the header files?

[Pierre Gergondet]

Thanks for bringing this up. I fixed it in the commit above (I confirmed I could build the standalone MultiContactController this way)