Classes that return allocated values now provide a free method

* zstr_free for strings
* zdir_flatten_free for file lists

This ensures frees are done in the same compile unit as mallocs,
which is necessary when using CZMQ in a DLL that may use a heap
separate from the caller's heap.
Merge pull request #280 from hintjens/master

Classes that return allocated values now provide a free method
zmonitor addition
Merge pull request #281 from claws/zmonitor_addition

zmonitor addition
Code cleanups
Merge pull request #282 from hintjens/master

Code cleanups
initial check in of new zproxy feature
fixing merge conflict between auto generated files concerning zmonitor and zproxy additions
adding initial generated documentation for the zproxy class
Merge pull request #283 from Talksum/master

initial check in of new zproxy feature
Whitespace fixes
Merge pull request #284 from hintjens/master

Whitespace fixes
Include zproxy in README
Merge pull request #286 from claws/zproxy-readme-update

Include zproxy in README
zproxy api adjustments (zproxy_bind now spawns attached thread and starts proxy) + test improvements
fixing merge conflict in zproxy.c
Merge pull request #287 from Talksum/master

zproxy api adjustments + test improvements
Added UUID support class
Merge pull request #288 from hintjens/master

Added UUID support class
Rebuild man pages