lib: Add a string.php file

Issue #69.
db.php: Add pip_db_table_create()

Issue #69.
Add an www/admin/ directory

Issue #69.
build: Add support for absolute paths in content hashing
_page.html: Add absolute paths for external content
Add an admin/setup.php File

Issue #69.
db.php: Use more explicit param names in pip_db_table_create()