Added 'vec::push_back' and 'vec::concretize'.
Moved ostream << std::array into the std:: namespace for ADL.
Added unit tests for vec::push_back().
progress/print_progress: added possibility not to output feedback on every iteration
Minor optimization of stddev.
Fixed typo.
Added 'match', 'collaspe' and 'system_var' functions.
Changed the default 'data_dir' to the 'PHYPP_DATA_DIR' environment variable.
Added 'filter_t', 'sed2flux', 'template_fit' and 'template_fit_renorm'.
Added 'match' unit test.
Removed useless code.
Overall performance improvements using move semantics in 'vec' and special behavior for unsigned indices.
Note that since functions like 'find', 'where', 'match' etc. now return unsigned indices, failure of matching is signaled by returning 'npos' (which is equal to -1 signed).
Optimized boolean operations by using move semantics.
Merge branch 'master' of https://github.com/cschreib/phypp

Conflicts:
	include/astro.hpp
	include/math.hpp