codegen: fixed generated gamedata header guards to comply with style guide
style: all header files now comply with header guard guidelines
codestyle: updated headerguard guideline in mom.h
added code compliance checker

automatically checks

 - header guards
 - legal header text
 - the author list
 - the third-party file list
 - copyright dates
doc: added test results for how converted units are affected by techs
codegen: now generates correct legal headers
copying.md: updated third-party file list, guidelines
legal: added legal header text to every single sourcefile

see copying.md for guidelines
refactored code compliance checker
Makefile: added 'check*' recipes, added 'check' to 'all'

recipies are used to invoke openage.codecompliance
buildsystem: added code compliance checker to .travis.yml
legal: added legal headers to all remaining files
Merge pull request #74 from mic-e/addlegalheaders

Add legal headers, code compliance checker