Additional instruction fixes
Tested and woring openSUSE instructions.
All information from BuildingOpenCaesar3.md has been duplicated or moved into README or the INSTALL files.
Additional instructions if the user compiled boost.
Fixed 7za instruction
Merge pull request #99 from Rovanion/install-instructions

Streamlining of install instructions
Merge branch 'master' of https://github.com/gecube/opencaesar3

Conflicts:
	INSTALL_LINUX : resolved using gecube/master
	README.md : resolved using gecube/master