New custom games and custom rules screen (#464)

* New waves and limited respawning option.

Added ability to manipulate number of respawns per wave. Added option to hold counting for next wave until all enemies are destroyed

* Critical bug fixed

Fixed frozen wave timer when rules.waitForWaveToEnd was enabled

* Requested changes

* Missed Import

* New custom game and custom rules screen

RulePreset is now a Gamemode (because each of them has a different goal).
New button under Gamemode selection which opens a dialog to modify rules of gamemode.
Now without any mutually exclusive options

* Requested changes

* Applied some text sugestions

* Wrong waveInProgress message displaying fixed

* Unwanted text

* Text changes

* I broke git

* Fixed chrash

* More fixes

New rule : manyCores; needed for sanbox mode

* Visual fix

* Requested changes #1 : small oversights

* Moved respawning logic to Player

and another imports cleanup

* manyCores in now attackMode

* UI changes

* Given back waves to sandbox and integer input in custom rules

* Renamed functions in CustomRulesScreen

* SPACES... Actually one space...

server/src/io/anuke/mindustry/server/ServerControl.java

@@ -204,11 +204,11 @@ public class ServerControl implements ApplicationListener{
                 return;
             }
 
-            RulePreset preset = RulePreset.survival;
+            Gamemode preset = Gamemode.survival;
 
             if(arg.length > 1){
                 try{
-                    preset = RulePreset.valueOf(arg[1]);
+                    preset = Gamemode.valueOf(arg[1]);
                 }catch(IllegalArgumentException e){
                     err("No gamemode '{0}' found.", arg[1]);
                     return;