sysPass 2.0-beta Bugfixes&Improvements

• [FIX] Fixed bug on file uploading
• [FIX] Fixed bug in Ajax request setup. Solves #372
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• [FIX] Set customer and category id when duplicated records are found during a CSV import. Fixes #372. Thanks to @anogues for the feedback
• [FIX] Fixed bug on DB structure export file.
• [MOD] Improved requests handling.
• [MOD] Improved security on backup tab. App Admin role is needed for download files
• [MOD] Catch exception message from CSV import and show it. Related #372
• [MOD] Improved critical error messages handling.
• [MOD] Improved master password changing process.
• [MOD] Improved backup process.
• [MOD] Improved init errors handling.
• [MOD] Improved Ajax request detect
• [ADD] New account private group feature (work in progress)
• [MOD] Improved linked account list retrieving by using Ajax
• [MOD] Minor tweaks