archipelago: Add info when retrying to get a lock
filed: Rename migrate option to pithos_migrate
docs: Minor typo fix regarding pithos_upgrade
Rename RST files for admin and installation guides
Rename RST files for admin, install and upgrade guides
docs: Update installation guide
docs: Explain Archipelago mapfile architecture
Merge pull request #24 from philipgian/feature-minorfixes

Feature minorfixes
Merge pull request #25 from Erethon/develop

Documentation updates