feat: allow for teleporting to player or relative position

[EmosewaMC]

tested with the following chat commands
updated the docs

[15-12-24 22:45:24 SlashCommandHandler.cpp:53] Handling command "tele" with args "EmosewaMC ~"
[15-12-24 22:45:29 SlashCommandHandler.cpp:53] Handling command "tele" with args "EmosewaMC candidmiracleflapjack"
[15-12-24 22:45:39 SlashCommandHandler.cpp:53] Handling command "tele" with args "candidmiracleflapjack emosewamc"
[15-12-24 22:45:41 SlashCommandHandler.cpp:53] Handling command "tele" with args "candidmiracleflapjack emosewamc"
[15-12-24 22:45:46 SlashCommandHandler.cpp:53] Handling command "tele" with args "EmosewaMC candidmiracleflapjack"
[15-12-24 22:45:53 SlashCommandHandler.cpp:53] Handling command "tele" with args "100 100"
[15-12-24 22:45:55 SlashCommandHandler.cpp:53] Handling command "tele" with args "100 100 100"
[15-12-24 22:46:04 SlashCommandHandler.cpp:53] Handling command "tele" with args "EmosewaMC 100"
[15-12-24 22:46:06 SlashCommandHandler.cpp:53] Handling command "tele" with args "EmosewaMC ~"
[15-12-24 22:46:13 SlashCommandHandler.cpp:53] Handling command "tele" with args "~ ~"
[15-12-24 22:46:18 SlashCommandHandler.cpp:53] Handling command "tele" with args "~ ~+10"
[15-12-24 22:46:20 SlashCommandHandler.cpp:53] Handling command "tele" with args "~-10 ~+10"
[15-12-24 22:46:27 SlashCommandHandler.cpp:53] Handling command "tele" with args "~ ~ ~\"
[15-12-24 22:46:28 SlashCommandHandler.cpp:53] Handling command "tele" with args "~ ~ ~"
[15-12-24 22:46:36 SlashCommandHandler.cpp:53] Handling command "tele" with args "~-10 ~+10 ~-10"
[15-12-24 22:46:45 SlashCommandHandler.cpp:53] Handling command "tele" with args "~-10 ~ ~-10"
[15-12-24 22:46:57 SlashCommandHandler.cpp:53] Handling command "tele" with args "~ ~+50 ~"
[15-12-24 22:47:01 SlashCommandHandler.cpp:53] Handling command "tele" with args "~ ~+100 ~"

[jadebenn]

Does this still preserve the option to teleport by coords?

[EmosewaMC]

Does this still preserve the option to teleport by coords?

lines 6 and 7 of the test cases test this