0.2.3

• rtrclient: increase polling period from 1 to 30 seconds
• rtrclient: bug fix for segfault caused by out-of-scope variable access
• rtrclient: fix wrong ssh example in usage output
• transport: remove const modifier from tr_ssh_config and tr_tcp_config struct members
• cmake: install doxygen documentation to $PREFIX/share/doc/rtrlib/
• add debian packaging files