DoubleX RMMV Action Cost Compatibility

Fixes DoubleX RMMV Action Cost compatibility issues

Addressed Plugins
DoubleX RMMV Popularized ATB Core
DoubleX RMMV Unison Item

*    # DoubleX RMMV Unison Item Config:                                      
 *      1. The action cost is the same for all unison actors                  
 *         - Reference tag: Unison Item Config Act Cost                       
 *         - Read <unison item actor act cost: costs> in DM.loadItemNotes     
 *         - Drawed the action cost in battle for each unison actor in        
 *           WIL.drawActCost and WSL.drawActCost                              
 *         - The default unison item action cost will be shown for all unison 
 *           actors when outside battles                                      
 *    # DoubleX RMMV Unison Item Default:                                     
 *      1. The number of action slot reserved by unison invokees are always 1 
 *         - Reference tag: Unison Item Default Invokee Act Slot Num          
 *         - Checked the action cost for each unison invokee in               
 *           GBB.canUseUnisonSkill and GBB.canUseUnisonItem as well           
 *         - Stored and restored the action cost for each unison invokee in   
 *           BM.addUnisonActors and BM.eraseUnisonActors as well              
 *    # (v1.00b+)DoubleX RMMV Popularized ATB Core:                           
 *      1. No battler can execute any action at all                           
 *         - Reference tag: PATB Act Validity                                 
 *         - Extended BattleManager.processTurn to ensure no valid actions    
 *           will be falsely regarded as invalid ones                         
 *    # (v1.00c+)DoubleX RMMV Popularized ATB Core:                           
 *      1. Battlers inputting skills/items with action cost greater than 1    
 *         remains inputable after finishing inputting all skills/items       
 *         - Reference tag: PATB Inputability                                 
 *         - Extended Game_Action.prototype.confirm_patb_item,                
 *           Scene_Battle.prototype.confirm_patb_act and added GBB.confirmAct 
 *           to confirm the reserved action slots as well

*      v1.00d(GMT 1500 11-8-2016):                                           
 *      1. Removed compatibility with DoubleX RMMV Minimalized ATB            
 *      1. In sync with the latest DoubleX RMMV Popularized ATB Core version  
 *      v1.00c(GMT 1000 5-6-2016):                                            
 *      1. Addressed more compatibility issues with                           
 *         - DoubleX RMMV Minimalized ATB                                     
 *         - DoubleX RMMV Popularized ATB Core                                
 *      v1.00b(GMT 0300 29-5-2016):                                           
 *      1. Addressed compatibility with                                       
 *         - DoubleX RMMV Minimalized ATB                                     
 *         - DoubleX RMMV Popularized ATB Core                                
 *      v1.00a(GMT 1500 22-5-2016):                                           
 *      1. 1st version of this plugin finished

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