Mouse-based "point-and-click" unit movement functionality implemented (finally!). Fixed calculations with alignToGrid() global function.
Added attackable tiles visuals after player unit's movement moves to destination.
Minor code cleanup.
Merge pull request #18 from mk200789/master

levelup system
Merge branch 'master' of https://github.com/chessmasterhong/WaterEmblem
Cleaned up experience and level up system. Fixed some incorrect property references in experience and level up system.
Reorganized media directory structure. Added cursor.png.
Modified menu display to return to main menu after unit's item equip/swap is completed.
Fixed bug where player units may "slide" past destination. Fixed player unit's direction animations for mouse movement.
Minor tweaks to enable entity detection.
Fixed bug with units not aligning to grid properly after reaching destination. Fixed bug with units' movement path not cleared after their turn ended.
Code cleanup and refactoring (moved sgn() function from global scope to encounter_zone.js, removed unused traces of realignToGrid() function, cleaned unnecessary code from experience system).
Updated records.
Added conditions for grid-snapping or free-moving cursor.
Added multiple tilesheet toggle based on grid or menu cursor.
Added task dependencies and requirements.