sysPass 2.0-beta Improvements

• [MOD] Improved logging messages handling.
• [MOD] Event logs are now logged in app lagnguage instead of user language.
• [MOD] Improved actions handling.
• [FIX] Minor bugfixes.
• [FIX] Fixed language selection for Polish. Related #124. Thanks to @wseredynski
• [ADD] Set fallback locale to en_US
• [MOD] Improved request handling.
• [MOD] Improved saved config parameters handling.
• [ADD]  Added Polish translation. Related #124. Thanks to @wseredynski
• [ADD]  Added Russian translation. Thanks to @titov
• [ADD]  Added Dutch translation. Thanks to @nlmaca
• [ADD]  Added language locale detection at config-info tab
• [MOD] UI tweaks
• [FIX]  Fixed JS bug with https and inverse proxy.