Makefile cleanup

[Nanoseb]

I have cleanup a bit the makefile compilation. As this changes a bit the current workflow (ie: where users store their personal compilation settings), I would understand if it was not something people wanted. But I found it cleaner and easier for anyone starting with this code base, in short here are the main changes:

• doesn't assume ~/bin and ~/lib are where you want the ow3d to be installed
• create build and install folders when needed
• make flags and parameters definable through environment variable with some default, and not in common.mk.
• overall code cleanup of the main makefile, more can probably be done, but I was not sure which target were used etc.

Hope this is useful, and happy to hear some feedback