Add Original Resource

From https://github.com/Akdeniz/google-play-crawler
Add some default setting files
Add categories config file
Add specific README of this API
Add Perl script for automatic craw the Google Play Market
Add a category folder.

category list move from pwd to pwd/categories
Remove unuse comment
Fix the comment of the if satement in the download_apk subroutine
Rename categories to categories.conf for AutoCrawler.pl
Fix typo. categories/
Do not create download dir if download dir already existed
Check md5sum for the current downloaded apk file.

If same as the apk file already existed in the system, remove the downloaded apk file.
If md5sum is different from the existed one, replace the old one with the new one.
Check if current dowloaded apk file is a new apk file not in the list or not
print log to the timestamp file and do the static of new and updated apk files
Add some comments for the code
Add time consumed result.
Fix the syntax
Print current downloading apk filename and deal with apk files cannot be found
Change name of load_top100 to load_top_n
Compute the number of old apk files.