iks: fixes in program options

+ server doesn't fail if config file is missing
+ base is marked as required
iks: cleanup connections naming

+ rename common 'connection' type name to slot_connection
iks: change szarp_dir to szarp_base in most places

+ szarp prefix directory is provided by SzarpWrapper class
+ iks knows only base name not exact directory
iks: Support for protocol changing

+ initialize application with welcome protocol
+ command 'hello' now gets szarp base as argument and if present switch
  to szbase protocol with chosen base
+ 'szbase' and 'welcome' are now protocols not locations
+ locations switching is now also available but not tested yet
+ move locations management to shared pointers
iks: fail response update

+ not sending quotes if fail message is empty
iks: support for szarp prefix

+ remove hard-coded /opt/szarp prefix
+ add option to server arguments to set szarp prefix
+ default prefix to compiled in PREFIX macro
+ move SzarpWrapper initailization to main function