Fix #571 libPMacc limits: 32 bit host

on 32bit hosts, size_t is the same as uint32_t (hopefully)
which declares the `max` for it twice.

Reported by @sigkill on github, thanks!
Update to New Modules on Hypnos
Incooperate Richards Feedback
Replace LWFA Eye Catcher with 3D Img
Add Benjamin Worpitz to Developers
Add Beta-RC6 Changelog
Fix Changelog Typos

thx @PrometheusPI for spotting them
thx @myJetLag for causing them
Fix an other typo, thx @n01r
Bump PIConGPU/png2gas to libSplash 1.2.3+

- makes PIConGPU (and png2gas) write fixed field-sizes (1.2.2+)
  -> should increase performance during writes/reads
- fixes a minor listing bug in libSplash (1.2.3+)
Merge pull request #582 from ComputationalRadiationPhysics/release-beta-rc6

Close #557 Beta-RC6 Release
Hotfix: CMake Boost 1.56.0+ is currently broken
Merge pull request #589 from ComputationalRadiationPhysics/master

Update dev with RC6 release changes