Implemented image upload api functionality.

 - Images are uploaded to a folder specifiled in local_setting.py file (see local_settings_template for example)
 - The view uses special file names generator which allows to avoid duplicates
 - Database schemachange included.

Refs, #152
Fixed small typo in code comment
Update ser.py

Implementing ThreadPoolExecutor approach in uploading images
Merge branch 'live' of github.com:OlegYarosh/pin into live
Merge branch 'live' of github.com:mygetlist/pin into live
Merge branch 'live' of github.com:OlegYarosh/pin into live
Layout changes
configure index.html layout
Merge branch 'live' of github.com:OlegYarosh/pin into live
Manage properties Image API method. #216
Categorize Image API method. #215
new feature method (first part) query in Image APIs
merging
'query' method in Image APIs
Query category Image API method. #213
Merge branch 'live' of github.com:OlegYarosh/pin into live
Added PIN_NEW_DAYS variable in config
Method for receiving hashtags for Image API. #212
resize big images in upload and tags implementation
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