gitsearchApp to gitSearchV2App :-(

This makes displaying metadata of an exercise
less verbose. Styling is a bit lacking as of now.

Restructure metadata translations of lists
to make declarations more concise.

added GitlabService.java to offer basic gitlab api functionalities like check if repo exists etc. , added check in StatisticsResource to avoid people sending get requests with IDs which not exist and therefore create lots of trash entities

added additional metadata fields -> difficulty, education level, status, type, version, format, keywords, requirements

layouting