Remove DB migrations which are no longer needed until some other DB changes will be made. Changed directory separator replacing to "/" to reflect gradle documentation

iOS memory fix -> maximum atlas size changed to 1024x1024. All images scaled down to maximum size 1000x1000.

 * gradle task for uploading SNAPSHOT assets package
 * using SNAPSHOT assets package only in devel build type and DEV versions

 * calculate assets zip files checksum and save to server
 * download zip file checksum
 * check of downloaded assets zip file integrity

 * new api for loading texture regions from atlases
 * removed old texture loader
 * gradle tasks for assets preparing
 * gradle UP-TO-DATE task check
 * application new api fix
 * atlases automatic linear filtering
 * sound assets conversion to flat hierarchy
 * automatic global assets loading
 * automatic screen and game local assets loading

 * gradle task for automatic creation of atlases from textures
 * refactored texture directory names

#14 Assets directory moved from ".tablexia" to ".tablexia/assets". Data directory moved from ".tablexia" to ".tablexia/data"

 * refactored mechanism of files access
 * new utility methods for file access

 * mechanism for calculating MD5 checksum for all directory (same mechanism used in ZipLoader and Gradle)