[FIX]: Multiple Amazon Games bugs

[imLinguin]

• Updated nile to store install size in installed.json
• Additionally I reproduced how nile creates folder names to avoid miss matches
• Changed how we determine if user is logged in, as username can be empty (added a fallback for login page to Unknown for that case)

Use the following Checklist if you have changed something on the Backend or Frontend:

• Tested the feature and it's working on a current and clean install.
• Tested the main App features and they are still working on a current and clean install. (Login, Install, Play, Uninstall, Move games, etc.)
• Created / Updated Tests (If necessary)
• Created / Updated documentation (If necessary)

[Nocccer]

LGTM. Left some suggestion to use removeSpecialcharacters function instead your own.