set_constant the send_target

fix bug 8049
http://hercules.ws/board/tracker/issue-8049-specialeffect-target-self-doesnt-work/
Merge pull request #265 from AnnieRuru/request_1

set_constant the send_target
Fixed Bug 8067

Sample plugin compiler error on msvc, credits to AnnieRuru (Thank you!)
http://hercules.ws/board/tracker/issue-8067-pluginsamplec-throws-error-on-microsoft-compiler/

Signed-off-by: shennetsind <ind@henn.et>
Merge branch 'master' of https://github.com/HerculesWS/Hercules
Fixed Bug 8072

Special Thanks to kyeme, Haruna
http://hercules.ws/board/tracker/issue-8072-map-crash-autotrade/

Signed-off-by: shennetsind <ind@henn.et>
Fixed getvariableofnpc

Would crash when target npc's variable database is empty.
Special Thanks to Haruna, ossi0110

Signed-off-by: shennetsind <ind@henn.et>
Added --load-plugin
Added --load-script