Provide support for querying common directories (temp, local, roaming, ...) #21

Provide cross-platform means for getting default locations for common uses such as:

• user profile related data (e.g., C:/Users/<user.name>/AppData/Roaming in windows)
• local application related data (e.g., C:/Users/<user.name>/AppData/Local in windows)
• local application with lower integrity level (e.g., C:/Users/<user.name>/AppData/LocalLow in windows)
• temporary data (e.g., C:/Users/<user.name>/AppData/Local/Temp in windows)
• user data/documents (e.g., C:/Users/<user.name>/Documents)
  and similarly for Games, Save Games, Music, Pictures, Videos, and Downloads...

Imo this should not (yet) cover/handle querying of locations for specific users, but refer to the current user (the user that started the program) instead.