Reorganization, make code human-readable

Renamed all sqlite3 dependent source files to reflect dependency
Renamed sqlite write functions to better state purpose (write new)
Reorganized order in which currency/account/transaction functions appear in source files
Commented all functions not considered self-explanitory
Bugfix in sqlite3-core

Fixed parameter ordering for call to sqlite3_snprintf
Implemented storage object routines

 - build_storage
 - destroy_storage
 - open_storage
 - close_storage

Also, helper routines
 - build_path
 - separate_file_from_path

Removed code from places which it no longer belonged