* fixed bug in vasprintf_append() causing the input string to stay unchanged
* fixed possible memleak in vasprintf_append() in case realloc fails
Merge pull request #124 from MarcelNehring/fg_string

Fixed bugs in vasprintf_append()
[Code Style] Added comments to option struct
Added ap_free call to end of programs and made arg parser static in controller+daemon.

This makes sure the arg parser lives as long as the program.
[Code Style] Added comments to parsing functions + Adapted function headers
Added function ap_is_used to check if option was specified on cmdline.
Added macro for unified parsing error messages.
[Code Style] Moved Brackets.
Added parameter "opt_string" to parsing functions.
Unified parsing using macro "PARSE_ERR". Also adapted "sscanf" calls.
[Code Style] Broke some lines.
Combined -h and --help option in controller.

-h can now use optional argument too (without blank after -h).
Changed -v --version output.

Added two macros for version output to common.h to be used in all other files.