Update build system to compile under git.

- build system use build dir and external_project dir out of source dir

- rename makefile.in.cmake to config.cmake

- fix missing armadillo_patch

- reporting information about sources in Flow123d version (WIP)
Add .gitignore
Fix reporting of build info.

- fix creation of rev_num.h , now it includes info about current git branch
- fix displaying of build info, display even wneh no input file is given
Fix wrong include and DBG indent.
Merge branch 'master' into build_system_for_git

Conflicts:
	.gitignore - add both